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3ed1f8a99d
sem_lock() did not properly pair memory barriers: !spin_is_locked() and spin_unlock_wait() are both only control barriers. The code needs an acquire barrier, otherwise the cpu might perform read operations before the lock test. As no primitive exists inside <include/spinlock.h> and since it seems noone wants another primitive, the code creates a local primitive within ipc/sem.c. With regards to -stable: The change of sem_wait_array() is a bugfix, the change to sem_lock() is a nop (just a preprocessor redefinition to improve the readability). The bugfix is necessary for all kernels that use sem_wait_array() (i.e.: starting from 3.10). Signed-off-by: Manfred Spraul <manfred@colorfullife.com> Reported-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Kirill Tkhai <ktkhai@parallels.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: <stable@vger.kernel.org> [3.10+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2212 lines
56 KiB
C
2212 lines
56 KiB
C
/*
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* linux/ipc/sem.c
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* Copyright (C) 1992 Krishna Balasubramanian
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* Copyright (C) 1995 Eric Schenk, Bruno Haible
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*
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* /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
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*
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* SMP-threaded, sysctl's added
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* (c) 1999 Manfred Spraul <manfred@colorfullife.com>
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* Enforced range limit on SEM_UNDO
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* (c) 2001 Red Hat Inc
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* Lockless wakeup
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* (c) 2003 Manfred Spraul <manfred@colorfullife.com>
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* Further wakeup optimizations, documentation
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* (c) 2010 Manfred Spraul <manfred@colorfullife.com>
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*
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* support for audit of ipc object properties and permission changes
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* Dustin Kirkland <dustin.kirkland@us.ibm.com>
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*
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* namespaces support
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* OpenVZ, SWsoft Inc.
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* Pavel Emelianov <xemul@openvz.org>
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*
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* Implementation notes: (May 2010)
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* This file implements System V semaphores.
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*
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* User space visible behavior:
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* - FIFO ordering for semop() operations (just FIFO, not starvation
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* protection)
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* - multiple semaphore operations that alter the same semaphore in
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* one semop() are handled.
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* - sem_ctime (time of last semctl()) is updated in the IPC_SET, SETVAL and
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* SETALL calls.
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* - two Linux specific semctl() commands: SEM_STAT, SEM_INFO.
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* - undo adjustments at process exit are limited to 0..SEMVMX.
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* - namespace are supported.
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* - SEMMSL, SEMMNS, SEMOPM and SEMMNI can be configured at runtine by writing
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* to /proc/sys/kernel/sem.
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* - statistics about the usage are reported in /proc/sysvipc/sem.
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*
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* Internals:
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* - scalability:
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* - all global variables are read-mostly.
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* - semop() calls and semctl(RMID) are synchronized by RCU.
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* - most operations do write operations (actually: spin_lock calls) to
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* the per-semaphore array structure.
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* Thus: Perfect SMP scaling between independent semaphore arrays.
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* If multiple semaphores in one array are used, then cache line
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* trashing on the semaphore array spinlock will limit the scaling.
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* - semncnt and semzcnt are calculated on demand in count_semcnt()
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* - the task that performs a successful semop() scans the list of all
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* sleeping tasks and completes any pending operations that can be fulfilled.
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* Semaphores are actively given to waiting tasks (necessary for FIFO).
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* (see update_queue())
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* - To improve the scalability, the actual wake-up calls are performed after
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* dropping all locks. (see wake_up_sem_queue_prepare(),
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* wake_up_sem_queue_do())
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* - All work is done by the waker, the woken up task does not have to do
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* anything - not even acquiring a lock or dropping a refcount.
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* - A woken up task may not even touch the semaphore array anymore, it may
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* have been destroyed already by a semctl(RMID).
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* - The synchronizations between wake-ups due to a timeout/signal and a
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* wake-up due to a completed semaphore operation is achieved by using an
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* intermediate state (IN_WAKEUP).
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* - UNDO values are stored in an array (one per process and per
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* semaphore array, lazily allocated). For backwards compatibility, multiple
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* modes for the UNDO variables are supported (per process, per thread)
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* (see copy_semundo, CLONE_SYSVSEM)
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* - There are two lists of the pending operations: a per-array list
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* and per-semaphore list (stored in the array). This allows to achieve FIFO
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* ordering without always scanning all pending operations.
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* The worst-case behavior is nevertheless O(N^2) for N wakeups.
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*/
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#include <linux/slab.h>
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#include <linux/spinlock.h>
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#include <linux/init.h>
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#include <linux/proc_fs.h>
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#include <linux/time.h>
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#include <linux/security.h>
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#include <linux/syscalls.h>
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#include <linux/audit.h>
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#include <linux/capability.h>
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#include <linux/seq_file.h>
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#include <linux/rwsem.h>
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#include <linux/nsproxy.h>
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#include <linux/ipc_namespace.h>
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#include <linux/uaccess.h>
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#include "util.h"
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/* One semaphore structure for each semaphore in the system. */
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struct sem {
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int semval; /* current value */
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int sempid; /* pid of last operation */
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spinlock_t lock; /* spinlock for fine-grained semtimedop */
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struct list_head pending_alter; /* pending single-sop operations */
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/* that alter the semaphore */
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struct list_head pending_const; /* pending single-sop operations */
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/* that do not alter the semaphore*/
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time_t sem_otime; /* candidate for sem_otime */
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} ____cacheline_aligned_in_smp;
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/* One queue for each sleeping process in the system. */
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struct sem_queue {
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struct list_head list; /* queue of pending operations */
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struct task_struct *sleeper; /* this process */
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struct sem_undo *undo; /* undo structure */
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int pid; /* process id of requesting process */
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int status; /* completion status of operation */
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struct sembuf *sops; /* array of pending operations */
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struct sembuf *blocking; /* the operation that blocked */
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int nsops; /* number of operations */
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int alter; /* does *sops alter the array? */
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};
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/* Each task has a list of undo requests. They are executed automatically
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* when the process exits.
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*/
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struct sem_undo {
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struct list_head list_proc; /* per-process list: *
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* all undos from one process
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* rcu protected */
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struct rcu_head rcu; /* rcu struct for sem_undo */
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struct sem_undo_list *ulp; /* back ptr to sem_undo_list */
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struct list_head list_id; /* per semaphore array list:
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* all undos for one array */
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int semid; /* semaphore set identifier */
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short *semadj; /* array of adjustments */
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/* one per semaphore */
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};
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/* sem_undo_list controls shared access to the list of sem_undo structures
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* that may be shared among all a CLONE_SYSVSEM task group.
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*/
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struct sem_undo_list {
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atomic_t refcnt;
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spinlock_t lock;
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struct list_head list_proc;
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};
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#define sem_ids(ns) ((ns)->ids[IPC_SEM_IDS])
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#define sem_checkid(sma, semid) ipc_checkid(&sma->sem_perm, semid)
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static int newary(struct ipc_namespace *, struct ipc_params *);
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static void freeary(struct ipc_namespace *, struct kern_ipc_perm *);
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#ifdef CONFIG_PROC_FS
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static int sysvipc_sem_proc_show(struct seq_file *s, void *it);
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#endif
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#define SEMMSL_FAST 256 /* 512 bytes on stack */
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#define SEMOPM_FAST 64 /* ~ 372 bytes on stack */
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/*
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* Locking:
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* sem_undo.id_next,
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* sem_array.complex_count,
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* sem_array.pending{_alter,_cont},
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* sem_array.sem_undo: global sem_lock() for read/write
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* sem_undo.proc_next: only "current" is allowed to read/write that field.
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*
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* sem_array.sem_base[i].pending_{const,alter}:
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* global or semaphore sem_lock() for read/write
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*/
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#define sc_semmsl sem_ctls[0]
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#define sc_semmns sem_ctls[1]
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#define sc_semopm sem_ctls[2]
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#define sc_semmni sem_ctls[3]
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void sem_init_ns(struct ipc_namespace *ns)
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{
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ns->sc_semmsl = SEMMSL;
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ns->sc_semmns = SEMMNS;
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ns->sc_semopm = SEMOPM;
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ns->sc_semmni = SEMMNI;
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ns->used_sems = 0;
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ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
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}
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#ifdef CONFIG_IPC_NS
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void sem_exit_ns(struct ipc_namespace *ns)
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{
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free_ipcs(ns, &sem_ids(ns), freeary);
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idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr);
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}
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#endif
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void __init sem_init(void)
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{
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sem_init_ns(&init_ipc_ns);
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ipc_init_proc_interface("sysvipc/sem",
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" key semid perms nsems uid gid cuid cgid otime ctime\n",
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IPC_SEM_IDS, sysvipc_sem_proc_show);
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}
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/**
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* unmerge_queues - unmerge queues, if possible.
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* @sma: semaphore array
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*
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* The function unmerges the wait queues if complex_count is 0.
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* It must be called prior to dropping the global semaphore array lock.
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*/
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static void unmerge_queues(struct sem_array *sma)
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{
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struct sem_queue *q, *tq;
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/* complex operations still around? */
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if (sma->complex_count)
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return;
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/*
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* We will switch back to simple mode.
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* Move all pending operation back into the per-semaphore
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* queues.
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*/
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list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
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struct sem *curr;
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curr = &sma->sem_base[q->sops[0].sem_num];
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list_add_tail(&q->list, &curr->pending_alter);
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}
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INIT_LIST_HEAD(&sma->pending_alter);
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}
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/**
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* merge_queues - merge single semop queues into global queue
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* @sma: semaphore array
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*
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* This function merges all per-semaphore queues into the global queue.
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* It is necessary to achieve FIFO ordering for the pending single-sop
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* operations when a multi-semop operation must sleep.
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* Only the alter operations must be moved, the const operations can stay.
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*/
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static void merge_queues(struct sem_array *sma)
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{
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int i;
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for (i = 0; i < sma->sem_nsems; i++) {
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struct sem *sem = sma->sem_base + i;
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list_splice_init(&sem->pending_alter, &sma->pending_alter);
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}
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}
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static void sem_rcu_free(struct rcu_head *head)
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{
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struct ipc_rcu *p = container_of(head, struct ipc_rcu, rcu);
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struct sem_array *sma = ipc_rcu_to_struct(p);
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security_sem_free(sma);
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ipc_rcu_free(head);
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}
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/*
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* spin_unlock_wait() and !spin_is_locked() are not memory barriers, they
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* are only control barriers.
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* The code must pair with spin_unlock(&sem->lock) or
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* spin_unlock(&sem_perm.lock), thus just the control barrier is insufficient.
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*
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* smp_rmb() is sufficient, as writes cannot pass the control barrier.
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*/
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#define ipc_smp_acquire__after_spin_is_unlocked() smp_rmb()
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/*
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* Wait until all currently ongoing simple ops have completed.
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* Caller must own sem_perm.lock.
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* New simple ops cannot start, because simple ops first check
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* that sem_perm.lock is free.
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* that a) sem_perm.lock is free and b) complex_count is 0.
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*/
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static void sem_wait_array(struct sem_array *sma)
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{
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int i;
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struct sem *sem;
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if (sma->complex_count) {
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/* The thread that increased sma->complex_count waited on
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* all sem->lock locks. Thus we don't need to wait again.
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*/
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return;
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}
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for (i = 0; i < sma->sem_nsems; i++) {
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sem = sma->sem_base + i;
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spin_unlock_wait(&sem->lock);
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}
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ipc_smp_acquire__after_spin_is_unlocked();
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}
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/*
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* If the request contains only one semaphore operation, and there are
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* no complex transactions pending, lock only the semaphore involved.
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* Otherwise, lock the entire semaphore array, since we either have
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* multiple semaphores in our own semops, or we need to look at
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* semaphores from other pending complex operations.
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*/
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static inline int sem_lock(struct sem_array *sma, struct sembuf *sops,
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int nsops)
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{
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struct sem *sem;
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if (nsops != 1) {
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/* Complex operation - acquire a full lock */
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ipc_lock_object(&sma->sem_perm);
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/* And wait until all simple ops that are processed
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* right now have dropped their locks.
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*/
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sem_wait_array(sma);
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return -1;
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}
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/*
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* Only one semaphore affected - try to optimize locking.
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* The rules are:
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* - optimized locking is possible if no complex operation
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* is either enqueued or processed right now.
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* - The test for enqueued complex ops is simple:
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* sma->complex_count != 0
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* - Testing for complex ops that are processed right now is
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* a bit more difficult. Complex ops acquire the full lock
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* and first wait that the running simple ops have completed.
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* (see above)
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* Thus: If we own a simple lock and the global lock is free
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* and complex_count is now 0, then it will stay 0 and
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* thus just locking sem->lock is sufficient.
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*/
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sem = sma->sem_base + sops->sem_num;
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if (sma->complex_count == 0) {
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/*
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* It appears that no complex operation is around.
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* Acquire the per-semaphore lock.
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*/
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spin_lock(&sem->lock);
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/* Then check that the global lock is free */
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if (!spin_is_locked(&sma->sem_perm.lock)) {
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/*
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* We need a memory barrier with acquire semantics,
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* otherwise we can race with another thread that does:
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* complex_count++;
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* spin_unlock(sem_perm.lock);
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*/
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ipc_smp_acquire__after_spin_is_unlocked();
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/*
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* Now repeat the test of complex_count:
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* It can't change anymore until we drop sem->lock.
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* Thus: if is now 0, then it will stay 0.
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*/
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if (sma->complex_count == 0) {
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/* fast path successful! */
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return sops->sem_num;
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}
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}
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spin_unlock(&sem->lock);
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}
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/* slow path: acquire the full lock */
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ipc_lock_object(&sma->sem_perm);
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if (sma->complex_count == 0) {
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/* False alarm:
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* There is no complex operation, thus we can switch
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* back to the fast path.
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*/
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spin_lock(&sem->lock);
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ipc_unlock_object(&sma->sem_perm);
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return sops->sem_num;
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} else {
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/* Not a false alarm, thus complete the sequence for a
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* full lock.
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*/
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sem_wait_array(sma);
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return -1;
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}
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}
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static inline void sem_unlock(struct sem_array *sma, int locknum)
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{
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if (locknum == -1) {
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unmerge_queues(sma);
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ipc_unlock_object(&sma->sem_perm);
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} else {
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struct sem *sem = sma->sem_base + locknum;
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spin_unlock(&sem->lock);
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}
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}
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/*
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* sem_lock_(check_) routines are called in the paths where the rwsem
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* is not held.
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*
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* The caller holds the RCU read lock.
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*/
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static inline struct sem_array *sem_obtain_lock(struct ipc_namespace *ns,
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int id, struct sembuf *sops, int nsops, int *locknum)
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{
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struct kern_ipc_perm *ipcp;
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struct sem_array *sma;
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ipcp = ipc_obtain_object_idr(&sem_ids(ns), id);
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if (IS_ERR(ipcp))
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return ERR_CAST(ipcp);
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sma = container_of(ipcp, struct sem_array, sem_perm);
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*locknum = sem_lock(sma, sops, nsops);
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/* ipc_rmid() may have already freed the ID while sem_lock
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* was spinning: verify that the structure is still valid
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*/
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if (ipc_valid_object(ipcp))
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return container_of(ipcp, struct sem_array, sem_perm);
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sem_unlock(sma, *locknum);
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return ERR_PTR(-EINVAL);
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}
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static inline struct sem_array *sem_obtain_object(struct ipc_namespace *ns, int id)
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{
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struct kern_ipc_perm *ipcp = ipc_obtain_object_idr(&sem_ids(ns), id);
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if (IS_ERR(ipcp))
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return ERR_CAST(ipcp);
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return container_of(ipcp, struct sem_array, sem_perm);
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}
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static inline struct sem_array *sem_obtain_object_check(struct ipc_namespace *ns,
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int id)
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{
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struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&sem_ids(ns), id);
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if (IS_ERR(ipcp))
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return ERR_CAST(ipcp);
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return container_of(ipcp, struct sem_array, sem_perm);
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}
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static inline void sem_lock_and_putref(struct sem_array *sma)
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{
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sem_lock(sma, NULL, -1);
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ipc_rcu_putref(sma, ipc_rcu_free);
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}
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static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
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{
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ipc_rmid(&sem_ids(ns), &s->sem_perm);
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}
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/*
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* Lockless wakeup algorithm:
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* Without the check/retry algorithm a lockless wakeup is possible:
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* - queue.status is initialized to -EINTR before blocking.
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* - wakeup is performed by
|
|
* * unlinking the queue entry from the pending list
|
|
* * setting queue.status to IN_WAKEUP
|
|
* This is the notification for the blocked thread that a
|
|
* result value is imminent.
|
|
* * call wake_up_process
|
|
* * set queue.status to the final value.
|
|
* - the previously blocked thread checks queue.status:
|
|
* * if it's IN_WAKEUP, then it must wait until the value changes
|
|
* * if it's not -EINTR, then the operation was completed by
|
|
* update_queue. semtimedop can return queue.status without
|
|
* performing any operation on the sem array.
|
|
* * otherwise it must acquire the spinlock and check what's up.
|
|
*
|
|
* The two-stage algorithm is necessary to protect against the following
|
|
* races:
|
|
* - if queue.status is set after wake_up_process, then the woken up idle
|
|
* thread could race forward and try (and fail) to acquire sma->lock
|
|
* before update_queue had a chance to set queue.status
|
|
* - if queue.status is written before wake_up_process and if the
|
|
* blocked process is woken up by a signal between writing
|
|
* queue.status and the wake_up_process, then the woken up
|
|
* process could return from semtimedop and die by calling
|
|
* sys_exit before wake_up_process is called. Then wake_up_process
|
|
* will oops, because the task structure is already invalid.
|
|
* (yes, this happened on s390 with sysv msg).
|
|
*
|
|
*/
|
|
#define IN_WAKEUP 1
|
|
|
|
/**
|
|
* newary - Create a new semaphore set
|
|
* @ns: namespace
|
|
* @params: ptr to the structure that contains key, semflg and nsems
|
|
*
|
|
* Called with sem_ids.rwsem held (as a writer)
|
|
*/
|
|
static int newary(struct ipc_namespace *ns, struct ipc_params *params)
|
|
{
|
|
int id;
|
|
int retval;
|
|
struct sem_array *sma;
|
|
int size;
|
|
key_t key = params->key;
|
|
int nsems = params->u.nsems;
|
|
int semflg = params->flg;
|
|
int i;
|
|
|
|
if (!nsems)
|
|
return -EINVAL;
|
|
if (ns->used_sems + nsems > ns->sc_semmns)
|
|
return -ENOSPC;
|
|
|
|
size = sizeof(*sma) + nsems * sizeof(struct sem);
|
|
sma = ipc_rcu_alloc(size);
|
|
if (!sma)
|
|
return -ENOMEM;
|
|
|
|
memset(sma, 0, size);
|
|
|
|
sma->sem_perm.mode = (semflg & S_IRWXUGO);
|
|
sma->sem_perm.key = key;
|
|
|
|
sma->sem_perm.security = NULL;
|
|
retval = security_sem_alloc(sma);
|
|
if (retval) {
|
|
ipc_rcu_putref(sma, ipc_rcu_free);
|
|
return retval;
|
|
}
|
|
|
|
sma->sem_base = (struct sem *) &sma[1];
|
|
|
|
for (i = 0; i < nsems; i++) {
|
|
INIT_LIST_HEAD(&sma->sem_base[i].pending_alter);
|
|
INIT_LIST_HEAD(&sma->sem_base[i].pending_const);
|
|
spin_lock_init(&sma->sem_base[i].lock);
|
|
}
|
|
|
|
sma->complex_count = 0;
|
|
INIT_LIST_HEAD(&sma->pending_alter);
|
|
INIT_LIST_HEAD(&sma->pending_const);
|
|
INIT_LIST_HEAD(&sma->list_id);
|
|
sma->sem_nsems = nsems;
|
|
sma->sem_ctime = get_seconds();
|
|
|
|
id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
|
|
if (id < 0) {
|
|
ipc_rcu_putref(sma, sem_rcu_free);
|
|
return id;
|
|
}
|
|
ns->used_sems += nsems;
|
|
|
|
sem_unlock(sma, -1);
|
|
rcu_read_unlock();
|
|
|
|
return sma->sem_perm.id;
|
|
}
|
|
|
|
|
|
/*
|
|
* Called with sem_ids.rwsem and ipcp locked.
|
|
*/
|
|
static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg)
|
|
{
|
|
struct sem_array *sma;
|
|
|
|
sma = container_of(ipcp, struct sem_array, sem_perm);
|
|
return security_sem_associate(sma, semflg);
|
|
}
|
|
|
|
/*
|
|
* Called with sem_ids.rwsem and ipcp locked.
|
|
*/
|
|
static inline int sem_more_checks(struct kern_ipc_perm *ipcp,
|
|
struct ipc_params *params)
|
|
{
|
|
struct sem_array *sma;
|
|
|
|
sma = container_of(ipcp, struct sem_array, sem_perm);
|
|
if (params->u.nsems > sma->sem_nsems)
|
|
return -EINVAL;
|
|
|
|
return 0;
|
|
}
|
|
|
|
SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
|
|
{
|
|
struct ipc_namespace *ns;
|
|
static const struct ipc_ops sem_ops = {
|
|
.getnew = newary,
|
|
.associate = sem_security,
|
|
.more_checks = sem_more_checks,
|
|
};
|
|
struct ipc_params sem_params;
|
|
|
|
ns = current->nsproxy->ipc_ns;
|
|
|
|
if (nsems < 0 || nsems > ns->sc_semmsl)
|
|
return -EINVAL;
|
|
|
|
sem_params.key = key;
|
|
sem_params.flg = semflg;
|
|
sem_params.u.nsems = nsems;
|
|
|
|
return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
|
|
}
|
|
|
|
/**
|
|
* perform_atomic_semop - Perform (if possible) a semaphore operation
|
|
* @sma: semaphore array
|
|
* @q: struct sem_queue that describes the operation
|
|
*
|
|
* Returns 0 if the operation was possible.
|
|
* Returns 1 if the operation is impossible, the caller must sleep.
|
|
* Negative values are error codes.
|
|
*/
|
|
static int perform_atomic_semop(struct sem_array *sma, struct sem_queue *q)
|
|
{
|
|
int result, sem_op, nsops, pid;
|
|
struct sembuf *sop;
|
|
struct sem *curr;
|
|
struct sembuf *sops;
|
|
struct sem_undo *un;
|
|
|
|
sops = q->sops;
|
|
nsops = q->nsops;
|
|
un = q->undo;
|
|
|
|
for (sop = sops; sop < sops + nsops; sop++) {
|
|
curr = sma->sem_base + sop->sem_num;
|
|
sem_op = sop->sem_op;
|
|
result = curr->semval;
|
|
|
|
if (!sem_op && result)
|
|
goto would_block;
|
|
|
|
result += sem_op;
|
|
if (result < 0)
|
|
goto would_block;
|
|
if (result > SEMVMX)
|
|
goto out_of_range;
|
|
|
|
if (sop->sem_flg & SEM_UNDO) {
|
|
int undo = un->semadj[sop->sem_num] - sem_op;
|
|
/* Exceeding the undo range is an error. */
|
|
if (undo < (-SEMAEM - 1) || undo > SEMAEM)
|
|
goto out_of_range;
|
|
un->semadj[sop->sem_num] = undo;
|
|
}
|
|
|
|
curr->semval = result;
|
|
}
|
|
|
|
sop--;
|
|
pid = q->pid;
|
|
while (sop >= sops) {
|
|
sma->sem_base[sop->sem_num].sempid = pid;
|
|
sop--;
|
|
}
|
|
|
|
return 0;
|
|
|
|
out_of_range:
|
|
result = -ERANGE;
|
|
goto undo;
|
|
|
|
would_block:
|
|
q->blocking = sop;
|
|
|
|
if (sop->sem_flg & IPC_NOWAIT)
|
|
result = -EAGAIN;
|
|
else
|
|
result = 1;
|
|
|
|
undo:
|
|
sop--;
|
|
while (sop >= sops) {
|
|
sem_op = sop->sem_op;
|
|
sma->sem_base[sop->sem_num].semval -= sem_op;
|
|
if (sop->sem_flg & SEM_UNDO)
|
|
un->semadj[sop->sem_num] += sem_op;
|
|
sop--;
|
|
}
|
|
|
|
return result;
|
|
}
|
|
|
|
/** wake_up_sem_queue_prepare(q, error): Prepare wake-up
|
|
* @q: queue entry that must be signaled
|
|
* @error: Error value for the signal
|
|
*
|
|
* Prepare the wake-up of the queue entry q.
|
|
*/
|
|
static void wake_up_sem_queue_prepare(struct list_head *pt,
|
|
struct sem_queue *q, int error)
|
|
{
|
|
if (list_empty(pt)) {
|
|
/*
|
|
* Hold preempt off so that we don't get preempted and have the
|
|
* wakee busy-wait until we're scheduled back on.
|
|
*/
|
|
preempt_disable();
|
|
}
|
|
q->status = IN_WAKEUP;
|
|
q->pid = error;
|
|
|
|
list_add_tail(&q->list, pt);
|
|
}
|
|
|
|
/**
|
|
* wake_up_sem_queue_do - do the actual wake-up
|
|
* @pt: list of tasks to be woken up
|
|
*
|
|
* Do the actual wake-up.
|
|
* The function is called without any locks held, thus the semaphore array
|
|
* could be destroyed already and the tasks can disappear as soon as the
|
|
* status is set to the actual return code.
|
|
*/
|
|
static void wake_up_sem_queue_do(struct list_head *pt)
|
|
{
|
|
struct sem_queue *q, *t;
|
|
int did_something;
|
|
|
|
did_something = !list_empty(pt);
|
|
list_for_each_entry_safe(q, t, pt, list) {
|
|
wake_up_process(q->sleeper);
|
|
/* q can disappear immediately after writing q->status. */
|
|
smp_wmb();
|
|
q->status = q->pid;
|
|
}
|
|
if (did_something)
|
|
preempt_enable();
|
|
}
|
|
|
|
static void unlink_queue(struct sem_array *sma, struct sem_queue *q)
|
|
{
|
|
list_del(&q->list);
|
|
if (q->nsops > 1)
|
|
sma->complex_count--;
|
|
}
|
|
|
|
/** check_restart(sma, q)
|
|
* @sma: semaphore array
|
|
* @q: the operation that just completed
|
|
*
|
|
* update_queue is O(N^2) when it restarts scanning the whole queue of
|
|
* waiting operations. Therefore this function checks if the restart is
|
|
* really necessary. It is called after a previously waiting operation
|
|
* modified the array.
|
|
* Note that wait-for-zero operations are handled without restart.
|
|
*/
|
|
static int check_restart(struct sem_array *sma, struct sem_queue *q)
|
|
{
|
|
/* pending complex alter operations are too difficult to analyse */
|
|
if (!list_empty(&sma->pending_alter))
|
|
return 1;
|
|
|
|
/* we were a sleeping complex operation. Too difficult */
|
|
if (q->nsops > 1)
|
|
return 1;
|
|
|
|
/* It is impossible that someone waits for the new value:
|
|
* - complex operations always restart.
|
|
* - wait-for-zero are handled seperately.
|
|
* - q is a previously sleeping simple operation that
|
|
* altered the array. It must be a decrement, because
|
|
* simple increments never sleep.
|
|
* - If there are older (higher priority) decrements
|
|
* in the queue, then they have observed the original
|
|
* semval value and couldn't proceed. The operation
|
|
* decremented to value - thus they won't proceed either.
|
|
*/
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* wake_const_ops - wake up non-alter tasks
|
|
* @sma: semaphore array.
|
|
* @semnum: semaphore that was modified.
|
|
* @pt: list head for the tasks that must be woken up.
|
|
*
|
|
* wake_const_ops must be called after a semaphore in a semaphore array
|
|
* was set to 0. If complex const operations are pending, wake_const_ops must
|
|
* be called with semnum = -1, as well as with the number of each modified
|
|
* semaphore.
|
|
* The tasks that must be woken up are added to @pt. The return code
|
|
* is stored in q->pid.
|
|
* The function returns 1 if at least one operation was completed successfully.
|
|
*/
|
|
static int wake_const_ops(struct sem_array *sma, int semnum,
|
|
struct list_head *pt)
|
|
{
|
|
struct sem_queue *q;
|
|
struct list_head *walk;
|
|
struct list_head *pending_list;
|
|
int semop_completed = 0;
|
|
|
|
if (semnum == -1)
|
|
pending_list = &sma->pending_const;
|
|
else
|
|
pending_list = &sma->sem_base[semnum].pending_const;
|
|
|
|
walk = pending_list->next;
|
|
while (walk != pending_list) {
|
|
int error;
|
|
|
|
q = container_of(walk, struct sem_queue, list);
|
|
walk = walk->next;
|
|
|
|
error = perform_atomic_semop(sma, q);
|
|
|
|
if (error <= 0) {
|
|
/* operation completed, remove from queue & wakeup */
|
|
|
|
unlink_queue(sma, q);
|
|
|
|
wake_up_sem_queue_prepare(pt, q, error);
|
|
if (error == 0)
|
|
semop_completed = 1;
|
|
}
|
|
}
|
|
return semop_completed;
|
|
}
|
|
|
|
/**
|
|
* do_smart_wakeup_zero - wakeup all wait for zero tasks
|
|
* @sma: semaphore array
|
|
* @sops: operations that were performed
|
|
* @nsops: number of operations
|
|
* @pt: list head of the tasks that must be woken up.
|
|
*
|
|
* Checks all required queue for wait-for-zero operations, based
|
|
* on the actual changes that were performed on the semaphore array.
|
|
* The function returns 1 if at least one operation was completed successfully.
|
|
*/
|
|
static int do_smart_wakeup_zero(struct sem_array *sma, struct sembuf *sops,
|
|
int nsops, struct list_head *pt)
|
|
{
|
|
int i;
|
|
int semop_completed = 0;
|
|
int got_zero = 0;
|
|
|
|
/* first: the per-semaphore queues, if known */
|
|
if (sops) {
|
|
for (i = 0; i < nsops; i++) {
|
|
int num = sops[i].sem_num;
|
|
|
|
if (sma->sem_base[num].semval == 0) {
|
|
got_zero = 1;
|
|
semop_completed |= wake_const_ops(sma, num, pt);
|
|
}
|
|
}
|
|
} else {
|
|
/*
|
|
* No sops means modified semaphores not known.
|
|
* Assume all were changed.
|
|
*/
|
|
for (i = 0; i < sma->sem_nsems; i++) {
|
|
if (sma->sem_base[i].semval == 0) {
|
|
got_zero = 1;
|
|
semop_completed |= wake_const_ops(sma, i, pt);
|
|
}
|
|
}
|
|
}
|
|
/*
|
|
* If one of the modified semaphores got 0,
|
|
* then check the global queue, too.
|
|
*/
|
|
if (got_zero)
|
|
semop_completed |= wake_const_ops(sma, -1, pt);
|
|
|
|
return semop_completed;
|
|
}
|
|
|
|
|
|
/**
|
|
* update_queue - look for tasks that can be completed.
|
|
* @sma: semaphore array.
|
|
* @semnum: semaphore that was modified.
|
|
* @pt: list head for the tasks that must be woken up.
|
|
*
|
|
* update_queue must be called after a semaphore in a semaphore array
|
|
* was modified. If multiple semaphores were modified, update_queue must
|
|
* be called with semnum = -1, as well as with the number of each modified
|
|
* semaphore.
|
|
* The tasks that must be woken up are added to @pt. The return code
|
|
* is stored in q->pid.
|
|
* The function internally checks if const operations can now succeed.
|
|
*
|
|
* The function return 1 if at least one semop was completed successfully.
|
|
*/
|
|
static int update_queue(struct sem_array *sma, int semnum, struct list_head *pt)
|
|
{
|
|
struct sem_queue *q;
|
|
struct list_head *walk;
|
|
struct list_head *pending_list;
|
|
int semop_completed = 0;
|
|
|
|
if (semnum == -1)
|
|
pending_list = &sma->pending_alter;
|
|
else
|
|
pending_list = &sma->sem_base[semnum].pending_alter;
|
|
|
|
again:
|
|
walk = pending_list->next;
|
|
while (walk != pending_list) {
|
|
int error, restart;
|
|
|
|
q = container_of(walk, struct sem_queue, list);
|
|
walk = walk->next;
|
|
|
|
/* If we are scanning the single sop, per-semaphore list of
|
|
* one semaphore and that semaphore is 0, then it is not
|
|
* necessary to scan further: simple increments
|
|
* that affect only one entry succeed immediately and cannot
|
|
* be in the per semaphore pending queue, and decrements
|
|
* cannot be successful if the value is already 0.
|
|
*/
|
|
if (semnum != -1 && sma->sem_base[semnum].semval == 0)
|
|
break;
|
|
|
|
error = perform_atomic_semop(sma, q);
|
|
|
|
/* Does q->sleeper still need to sleep? */
|
|
if (error > 0)
|
|
continue;
|
|
|
|
unlink_queue(sma, q);
|
|
|
|
if (error) {
|
|
restart = 0;
|
|
} else {
|
|
semop_completed = 1;
|
|
do_smart_wakeup_zero(sma, q->sops, q->nsops, pt);
|
|
restart = check_restart(sma, q);
|
|
}
|
|
|
|
wake_up_sem_queue_prepare(pt, q, error);
|
|
if (restart)
|
|
goto again;
|
|
}
|
|
return semop_completed;
|
|
}
|
|
|
|
/**
|
|
* set_semotime - set sem_otime
|
|
* @sma: semaphore array
|
|
* @sops: operations that modified the array, may be NULL
|
|
*
|
|
* sem_otime is replicated to avoid cache line trashing.
|
|
* This function sets one instance to the current time.
|
|
*/
|
|
static void set_semotime(struct sem_array *sma, struct sembuf *sops)
|
|
{
|
|
if (sops == NULL) {
|
|
sma->sem_base[0].sem_otime = get_seconds();
|
|
} else {
|
|
sma->sem_base[sops[0].sem_num].sem_otime =
|
|
get_seconds();
|
|
}
|
|
}
|
|
|
|
/**
|
|
* do_smart_update - optimized update_queue
|
|
* @sma: semaphore array
|
|
* @sops: operations that were performed
|
|
* @nsops: number of operations
|
|
* @otime: force setting otime
|
|
* @pt: list head of the tasks that must be woken up.
|
|
*
|
|
* do_smart_update() does the required calls to update_queue and wakeup_zero,
|
|
* based on the actual changes that were performed on the semaphore array.
|
|
* Note that the function does not do the actual wake-up: the caller is
|
|
* responsible for calling wake_up_sem_queue_do(@pt).
|
|
* It is safe to perform this call after dropping all locks.
|
|
*/
|
|
static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops,
|
|
int otime, struct list_head *pt)
|
|
{
|
|
int i;
|
|
|
|
otime |= do_smart_wakeup_zero(sma, sops, nsops, pt);
|
|
|
|
if (!list_empty(&sma->pending_alter)) {
|
|
/* semaphore array uses the global queue - just process it. */
|
|
otime |= update_queue(sma, -1, pt);
|
|
} else {
|
|
if (!sops) {
|
|
/*
|
|
* No sops, thus the modified semaphores are not
|
|
* known. Check all.
|
|
*/
|
|
for (i = 0; i < sma->sem_nsems; i++)
|
|
otime |= update_queue(sma, i, pt);
|
|
} else {
|
|
/*
|
|
* Check the semaphores that were increased:
|
|
* - No complex ops, thus all sleeping ops are
|
|
* decrease.
|
|
* - if we decreased the value, then any sleeping
|
|
* semaphore ops wont be able to run: If the
|
|
* previous value was too small, then the new
|
|
* value will be too small, too.
|
|
*/
|
|
for (i = 0; i < nsops; i++) {
|
|
if (sops[i].sem_op > 0) {
|
|
otime |= update_queue(sma,
|
|
sops[i].sem_num, pt);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
if (otime)
|
|
set_semotime(sma, sops);
|
|
}
|
|
|
|
/*
|
|
* check_qop: Test if a queued operation sleeps on the semaphore semnum
|
|
*/
|
|
static int check_qop(struct sem_array *sma, int semnum, struct sem_queue *q,
|
|
bool count_zero)
|
|
{
|
|
struct sembuf *sop = q->blocking;
|
|
|
|
/*
|
|
* Linux always (since 0.99.10) reported a task as sleeping on all
|
|
* semaphores. This violates SUS, therefore it was changed to the
|
|
* standard compliant behavior.
|
|
* Give the administrators a chance to notice that an application
|
|
* might misbehave because it relies on the Linux behavior.
|
|
*/
|
|
pr_info_once("semctl(GETNCNT/GETZCNT) is since 3.16 Single Unix Specification compliant.\n"
|
|
"The task %s (%d) triggered the difference, watch for misbehavior.\n",
|
|
current->comm, task_pid_nr(current));
|
|
|
|
if (sop->sem_num != semnum)
|
|
return 0;
|
|
|
|
if (count_zero && sop->sem_op == 0)
|
|
return 1;
|
|
if (!count_zero && sop->sem_op < 0)
|
|
return 1;
|
|
|
|
return 0;
|
|
}
|
|
|
|
/* The following counts are associated to each semaphore:
|
|
* semncnt number of tasks waiting on semval being nonzero
|
|
* semzcnt number of tasks waiting on semval being zero
|
|
*
|
|
* Per definition, a task waits only on the semaphore of the first semop
|
|
* that cannot proceed, even if additional operation would block, too.
|
|
*/
|
|
static int count_semcnt(struct sem_array *sma, ushort semnum,
|
|
bool count_zero)
|
|
{
|
|
struct list_head *l;
|
|
struct sem_queue *q;
|
|
int semcnt;
|
|
|
|
semcnt = 0;
|
|
/* First: check the simple operations. They are easy to evaluate */
|
|
if (count_zero)
|
|
l = &sma->sem_base[semnum].pending_const;
|
|
else
|
|
l = &sma->sem_base[semnum].pending_alter;
|
|
|
|
list_for_each_entry(q, l, list) {
|
|
/* all task on a per-semaphore list sleep on exactly
|
|
* that semaphore
|
|
*/
|
|
semcnt++;
|
|
}
|
|
|
|
/* Then: check the complex operations. */
|
|
list_for_each_entry(q, &sma->pending_alter, list) {
|
|
semcnt += check_qop(sma, semnum, q, count_zero);
|
|
}
|
|
if (count_zero) {
|
|
list_for_each_entry(q, &sma->pending_const, list) {
|
|
semcnt += check_qop(sma, semnum, q, count_zero);
|
|
}
|
|
}
|
|
return semcnt;
|
|
}
|
|
|
|
/* Free a semaphore set. freeary() is called with sem_ids.rwsem locked
|
|
* as a writer and the spinlock for this semaphore set hold. sem_ids.rwsem
|
|
* remains locked on exit.
|
|
*/
|
|
static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
|
|
{
|
|
struct sem_undo *un, *tu;
|
|
struct sem_queue *q, *tq;
|
|
struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
|
|
struct list_head tasks;
|
|
int i;
|
|
|
|
/* Free the existing undo structures for this semaphore set. */
|
|
ipc_assert_locked_object(&sma->sem_perm);
|
|
list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
|
|
list_del(&un->list_id);
|
|
spin_lock(&un->ulp->lock);
|
|
un->semid = -1;
|
|
list_del_rcu(&un->list_proc);
|
|
spin_unlock(&un->ulp->lock);
|
|
kfree_rcu(un, rcu);
|
|
}
|
|
|
|
/* Wake up all pending processes and let them fail with EIDRM. */
|
|
INIT_LIST_HEAD(&tasks);
|
|
list_for_each_entry_safe(q, tq, &sma->pending_const, list) {
|
|
unlink_queue(sma, q);
|
|
wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
|
|
}
|
|
|
|
list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
|
|
unlink_queue(sma, q);
|
|
wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
|
|
}
|
|
for (i = 0; i < sma->sem_nsems; i++) {
|
|
struct sem *sem = sma->sem_base + i;
|
|
list_for_each_entry_safe(q, tq, &sem->pending_const, list) {
|
|
unlink_queue(sma, q);
|
|
wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
|
|
}
|
|
list_for_each_entry_safe(q, tq, &sem->pending_alter, list) {
|
|
unlink_queue(sma, q);
|
|
wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
|
|
}
|
|
}
|
|
|
|
/* Remove the semaphore set from the IDR */
|
|
sem_rmid(ns, sma);
|
|
sem_unlock(sma, -1);
|
|
rcu_read_unlock();
|
|
|
|
wake_up_sem_queue_do(&tasks);
|
|
ns->used_sems -= sma->sem_nsems;
|
|
ipc_rcu_putref(sma, sem_rcu_free);
|
|
}
|
|
|
|
static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
|
|
{
|
|
switch (version) {
|
|
case IPC_64:
|
|
return copy_to_user(buf, in, sizeof(*in));
|
|
case IPC_OLD:
|
|
{
|
|
struct semid_ds out;
|
|
|
|
memset(&out, 0, sizeof(out));
|
|
|
|
ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
|
|
|
|
out.sem_otime = in->sem_otime;
|
|
out.sem_ctime = in->sem_ctime;
|
|
out.sem_nsems = in->sem_nsems;
|
|
|
|
return copy_to_user(buf, &out, sizeof(out));
|
|
}
|
|
default:
|
|
return -EINVAL;
|
|
}
|
|
}
|
|
|
|
static time_t get_semotime(struct sem_array *sma)
|
|
{
|
|
int i;
|
|
time_t res;
|
|
|
|
res = sma->sem_base[0].sem_otime;
|
|
for (i = 1; i < sma->sem_nsems; i++) {
|
|
time_t to = sma->sem_base[i].sem_otime;
|
|
|
|
if (to > res)
|
|
res = to;
|
|
}
|
|
return res;
|
|
}
|
|
|
|
static int semctl_nolock(struct ipc_namespace *ns, int semid,
|
|
int cmd, int version, void __user *p)
|
|
{
|
|
int err;
|
|
struct sem_array *sma;
|
|
|
|
switch (cmd) {
|
|
case IPC_INFO:
|
|
case SEM_INFO:
|
|
{
|
|
struct seminfo seminfo;
|
|
int max_id;
|
|
|
|
err = security_sem_semctl(NULL, cmd);
|
|
if (err)
|
|
return err;
|
|
|
|
memset(&seminfo, 0, sizeof(seminfo));
|
|
seminfo.semmni = ns->sc_semmni;
|
|
seminfo.semmns = ns->sc_semmns;
|
|
seminfo.semmsl = ns->sc_semmsl;
|
|
seminfo.semopm = ns->sc_semopm;
|
|
seminfo.semvmx = SEMVMX;
|
|
seminfo.semmnu = SEMMNU;
|
|
seminfo.semmap = SEMMAP;
|
|
seminfo.semume = SEMUME;
|
|
down_read(&sem_ids(ns).rwsem);
|
|
if (cmd == SEM_INFO) {
|
|
seminfo.semusz = sem_ids(ns).in_use;
|
|
seminfo.semaem = ns->used_sems;
|
|
} else {
|
|
seminfo.semusz = SEMUSZ;
|
|
seminfo.semaem = SEMAEM;
|
|
}
|
|
max_id = ipc_get_maxid(&sem_ids(ns));
|
|
up_read(&sem_ids(ns).rwsem);
|
|
if (copy_to_user(p, &seminfo, sizeof(struct seminfo)))
|
|
return -EFAULT;
|
|
return (max_id < 0) ? 0 : max_id;
|
|
}
|
|
case IPC_STAT:
|
|
case SEM_STAT:
|
|
{
|
|
struct semid64_ds tbuf;
|
|
int id = 0;
|
|
|
|
memset(&tbuf, 0, sizeof(tbuf));
|
|
|
|
rcu_read_lock();
|
|
if (cmd == SEM_STAT) {
|
|
sma = sem_obtain_object(ns, semid);
|
|
if (IS_ERR(sma)) {
|
|
err = PTR_ERR(sma);
|
|
goto out_unlock;
|
|
}
|
|
id = sma->sem_perm.id;
|
|
} else {
|
|
sma = sem_obtain_object_check(ns, semid);
|
|
if (IS_ERR(sma)) {
|
|
err = PTR_ERR(sma);
|
|
goto out_unlock;
|
|
}
|
|
}
|
|
|
|
err = -EACCES;
|
|
if (ipcperms(ns, &sma->sem_perm, S_IRUGO))
|
|
goto out_unlock;
|
|
|
|
err = security_sem_semctl(sma, cmd);
|
|
if (err)
|
|
goto out_unlock;
|
|
|
|
kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
|
|
tbuf.sem_otime = get_semotime(sma);
|
|
tbuf.sem_ctime = sma->sem_ctime;
|
|
tbuf.sem_nsems = sma->sem_nsems;
|
|
rcu_read_unlock();
|
|
if (copy_semid_to_user(p, &tbuf, version))
|
|
return -EFAULT;
|
|
return id;
|
|
}
|
|
default:
|
|
return -EINVAL;
|
|
}
|
|
out_unlock:
|
|
rcu_read_unlock();
|
|
return err;
|
|
}
|
|
|
|
static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum,
|
|
unsigned long arg)
|
|
{
|
|
struct sem_undo *un;
|
|
struct sem_array *sma;
|
|
struct sem *curr;
|
|
int err;
|
|
struct list_head tasks;
|
|
int val;
|
|
#if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN)
|
|
/* big-endian 64bit */
|
|
val = arg >> 32;
|
|
#else
|
|
/* 32bit or little-endian 64bit */
|
|
val = arg;
|
|
#endif
|
|
|
|
if (val > SEMVMX || val < 0)
|
|
return -ERANGE;
|
|
|
|
INIT_LIST_HEAD(&tasks);
|
|
|
|
rcu_read_lock();
|
|
sma = sem_obtain_object_check(ns, semid);
|
|
if (IS_ERR(sma)) {
|
|
rcu_read_unlock();
|
|
return PTR_ERR(sma);
|
|
}
|
|
|
|
if (semnum < 0 || semnum >= sma->sem_nsems) {
|
|
rcu_read_unlock();
|
|
return -EINVAL;
|
|
}
|
|
|
|
|
|
if (ipcperms(ns, &sma->sem_perm, S_IWUGO)) {
|
|
rcu_read_unlock();
|
|
return -EACCES;
|
|
}
|
|
|
|
err = security_sem_semctl(sma, SETVAL);
|
|
if (err) {
|
|
rcu_read_unlock();
|
|
return -EACCES;
|
|
}
|
|
|
|
sem_lock(sma, NULL, -1);
|
|
|
|
if (!ipc_valid_object(&sma->sem_perm)) {
|
|
sem_unlock(sma, -1);
|
|
rcu_read_unlock();
|
|
return -EIDRM;
|
|
}
|
|
|
|
curr = &sma->sem_base[semnum];
|
|
|
|
ipc_assert_locked_object(&sma->sem_perm);
|
|
list_for_each_entry(un, &sma->list_id, list_id)
|
|
un->semadj[semnum] = 0;
|
|
|
|
curr->semval = val;
|
|
curr->sempid = task_tgid_vnr(current);
|
|
sma->sem_ctime = get_seconds();
|
|
/* maybe some queued-up processes were waiting for this */
|
|
do_smart_update(sma, NULL, 0, 0, &tasks);
|
|
sem_unlock(sma, -1);
|
|
rcu_read_unlock();
|
|
wake_up_sem_queue_do(&tasks);
|
|
return 0;
|
|
}
|
|
|
|
static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
|
|
int cmd, void __user *p)
|
|
{
|
|
struct sem_array *sma;
|
|
struct sem *curr;
|
|
int err, nsems;
|
|
ushort fast_sem_io[SEMMSL_FAST];
|
|
ushort *sem_io = fast_sem_io;
|
|
struct list_head tasks;
|
|
|
|
INIT_LIST_HEAD(&tasks);
|
|
|
|
rcu_read_lock();
|
|
sma = sem_obtain_object_check(ns, semid);
|
|
if (IS_ERR(sma)) {
|
|
rcu_read_unlock();
|
|
return PTR_ERR(sma);
|
|
}
|
|
|
|
nsems = sma->sem_nsems;
|
|
|
|
err = -EACCES;
|
|
if (ipcperms(ns, &sma->sem_perm, cmd == SETALL ? S_IWUGO : S_IRUGO))
|
|
goto out_rcu_wakeup;
|
|
|
|
err = security_sem_semctl(sma, cmd);
|
|
if (err)
|
|
goto out_rcu_wakeup;
|
|
|
|
err = -EACCES;
|
|
switch (cmd) {
|
|
case GETALL:
|
|
{
|
|
ushort __user *array = p;
|
|
int i;
|
|
|
|
sem_lock(sma, NULL, -1);
|
|
if (!ipc_valid_object(&sma->sem_perm)) {
|
|
err = -EIDRM;
|
|
goto out_unlock;
|
|
}
|
|
if (nsems > SEMMSL_FAST) {
|
|
if (!ipc_rcu_getref(sma)) {
|
|
err = -EIDRM;
|
|
goto out_unlock;
|
|
}
|
|
sem_unlock(sma, -1);
|
|
rcu_read_unlock();
|
|
sem_io = ipc_alloc(sizeof(ushort)*nsems);
|
|
if (sem_io == NULL) {
|
|
ipc_rcu_putref(sma, ipc_rcu_free);
|
|
return -ENOMEM;
|
|
}
|
|
|
|
rcu_read_lock();
|
|
sem_lock_and_putref(sma);
|
|
if (!ipc_valid_object(&sma->sem_perm)) {
|
|
err = -EIDRM;
|
|
goto out_unlock;
|
|
}
|
|
}
|
|
for (i = 0; i < sma->sem_nsems; i++)
|
|
sem_io[i] = sma->sem_base[i].semval;
|
|
sem_unlock(sma, -1);
|
|
rcu_read_unlock();
|
|
err = 0;
|
|
if (copy_to_user(array, sem_io, nsems*sizeof(ushort)))
|
|
err = -EFAULT;
|
|
goto out_free;
|
|
}
|
|
case SETALL:
|
|
{
|
|
int i;
|
|
struct sem_undo *un;
|
|
|
|
if (!ipc_rcu_getref(sma)) {
|
|
err = -EIDRM;
|
|
goto out_rcu_wakeup;
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
if (nsems > SEMMSL_FAST) {
|
|
sem_io = ipc_alloc(sizeof(ushort)*nsems);
|
|
if (sem_io == NULL) {
|
|
ipc_rcu_putref(sma, ipc_rcu_free);
|
|
return -ENOMEM;
|
|
}
|
|
}
|
|
|
|
if (copy_from_user(sem_io, p, nsems*sizeof(ushort))) {
|
|
ipc_rcu_putref(sma, ipc_rcu_free);
|
|
err = -EFAULT;
|
|
goto out_free;
|
|
}
|
|
|
|
for (i = 0; i < nsems; i++) {
|
|
if (sem_io[i] > SEMVMX) {
|
|
ipc_rcu_putref(sma, ipc_rcu_free);
|
|
err = -ERANGE;
|
|
goto out_free;
|
|
}
|
|
}
|
|
rcu_read_lock();
|
|
sem_lock_and_putref(sma);
|
|
if (!ipc_valid_object(&sma->sem_perm)) {
|
|
err = -EIDRM;
|
|
goto out_unlock;
|
|
}
|
|
|
|
for (i = 0; i < nsems; i++)
|
|
sma->sem_base[i].semval = sem_io[i];
|
|
|
|
ipc_assert_locked_object(&sma->sem_perm);
|
|
list_for_each_entry(un, &sma->list_id, list_id) {
|
|
for (i = 0; i < nsems; i++)
|
|
un->semadj[i] = 0;
|
|
}
|
|
sma->sem_ctime = get_seconds();
|
|
/* maybe some queued-up processes were waiting for this */
|
|
do_smart_update(sma, NULL, 0, 0, &tasks);
|
|
err = 0;
|
|
goto out_unlock;
|
|
}
|
|
/* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */
|
|
}
|
|
err = -EINVAL;
|
|
if (semnum < 0 || semnum >= nsems)
|
|
goto out_rcu_wakeup;
|
|
|
|
sem_lock(sma, NULL, -1);
|
|
if (!ipc_valid_object(&sma->sem_perm)) {
|
|
err = -EIDRM;
|
|
goto out_unlock;
|
|
}
|
|
curr = &sma->sem_base[semnum];
|
|
|
|
switch (cmd) {
|
|
case GETVAL:
|
|
err = curr->semval;
|
|
goto out_unlock;
|
|
case GETPID:
|
|
err = curr->sempid;
|
|
goto out_unlock;
|
|
case GETNCNT:
|
|
err = count_semcnt(sma, semnum, 0);
|
|
goto out_unlock;
|
|
case GETZCNT:
|
|
err = count_semcnt(sma, semnum, 1);
|
|
goto out_unlock;
|
|
}
|
|
|
|
out_unlock:
|
|
sem_unlock(sma, -1);
|
|
out_rcu_wakeup:
|
|
rcu_read_unlock();
|
|
wake_up_sem_queue_do(&tasks);
|
|
out_free:
|
|
if (sem_io != fast_sem_io)
|
|
ipc_free(sem_io, sizeof(ushort)*nsems);
|
|
return err;
|
|
}
|
|
|
|
static inline unsigned long
|
|
copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
|
|
{
|
|
switch (version) {
|
|
case IPC_64:
|
|
if (copy_from_user(out, buf, sizeof(*out)))
|
|
return -EFAULT;
|
|
return 0;
|
|
case IPC_OLD:
|
|
{
|
|
struct semid_ds tbuf_old;
|
|
|
|
if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
|
|
return -EFAULT;
|
|
|
|
out->sem_perm.uid = tbuf_old.sem_perm.uid;
|
|
out->sem_perm.gid = tbuf_old.sem_perm.gid;
|
|
out->sem_perm.mode = tbuf_old.sem_perm.mode;
|
|
|
|
return 0;
|
|
}
|
|
default:
|
|
return -EINVAL;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* This function handles some semctl commands which require the rwsem
|
|
* to be held in write mode.
|
|
* NOTE: no locks must be held, the rwsem is taken inside this function.
|
|
*/
|
|
static int semctl_down(struct ipc_namespace *ns, int semid,
|
|
int cmd, int version, void __user *p)
|
|
{
|
|
struct sem_array *sma;
|
|
int err;
|
|
struct semid64_ds semid64;
|
|
struct kern_ipc_perm *ipcp;
|
|
|
|
if (cmd == IPC_SET) {
|
|
if (copy_semid_from_user(&semid64, p, version))
|
|
return -EFAULT;
|
|
}
|
|
|
|
down_write(&sem_ids(ns).rwsem);
|
|
rcu_read_lock();
|
|
|
|
ipcp = ipcctl_pre_down_nolock(ns, &sem_ids(ns), semid, cmd,
|
|
&semid64.sem_perm, 0);
|
|
if (IS_ERR(ipcp)) {
|
|
err = PTR_ERR(ipcp);
|
|
goto out_unlock1;
|
|
}
|
|
|
|
sma = container_of(ipcp, struct sem_array, sem_perm);
|
|
|
|
err = security_sem_semctl(sma, cmd);
|
|
if (err)
|
|
goto out_unlock1;
|
|
|
|
switch (cmd) {
|
|
case IPC_RMID:
|
|
sem_lock(sma, NULL, -1);
|
|
/* freeary unlocks the ipc object and rcu */
|
|
freeary(ns, ipcp);
|
|
goto out_up;
|
|
case IPC_SET:
|
|
sem_lock(sma, NULL, -1);
|
|
err = ipc_update_perm(&semid64.sem_perm, ipcp);
|
|
if (err)
|
|
goto out_unlock0;
|
|
sma->sem_ctime = get_seconds();
|
|
break;
|
|
default:
|
|
err = -EINVAL;
|
|
goto out_unlock1;
|
|
}
|
|
|
|
out_unlock0:
|
|
sem_unlock(sma, -1);
|
|
out_unlock1:
|
|
rcu_read_unlock();
|
|
out_up:
|
|
up_write(&sem_ids(ns).rwsem);
|
|
return err;
|
|
}
|
|
|
|
SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
|
|
{
|
|
int version;
|
|
struct ipc_namespace *ns;
|
|
void __user *p = (void __user *)arg;
|
|
|
|
if (semid < 0)
|
|
return -EINVAL;
|
|
|
|
version = ipc_parse_version(&cmd);
|
|
ns = current->nsproxy->ipc_ns;
|
|
|
|
switch (cmd) {
|
|
case IPC_INFO:
|
|
case SEM_INFO:
|
|
case IPC_STAT:
|
|
case SEM_STAT:
|
|
return semctl_nolock(ns, semid, cmd, version, p);
|
|
case GETALL:
|
|
case GETVAL:
|
|
case GETPID:
|
|
case GETNCNT:
|
|
case GETZCNT:
|
|
case SETALL:
|
|
return semctl_main(ns, semid, semnum, cmd, p);
|
|
case SETVAL:
|
|
return semctl_setval(ns, semid, semnum, arg);
|
|
case IPC_RMID:
|
|
case IPC_SET:
|
|
return semctl_down(ns, semid, cmd, version, p);
|
|
default:
|
|
return -EINVAL;
|
|
}
|
|
}
|
|
|
|
/* If the task doesn't already have a undo_list, then allocate one
|
|
* here. We guarantee there is only one thread using this undo list,
|
|
* and current is THE ONE
|
|
*
|
|
* If this allocation and assignment succeeds, but later
|
|
* portions of this code fail, there is no need to free the sem_undo_list.
|
|
* Just let it stay associated with the task, and it'll be freed later
|
|
* at exit time.
|
|
*
|
|
* This can block, so callers must hold no locks.
|
|
*/
|
|
static inline int get_undo_list(struct sem_undo_list **undo_listp)
|
|
{
|
|
struct sem_undo_list *undo_list;
|
|
|
|
undo_list = current->sysvsem.undo_list;
|
|
if (!undo_list) {
|
|
undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
|
|
if (undo_list == NULL)
|
|
return -ENOMEM;
|
|
spin_lock_init(&undo_list->lock);
|
|
atomic_set(&undo_list->refcnt, 1);
|
|
INIT_LIST_HEAD(&undo_list->list_proc);
|
|
|
|
current->sysvsem.undo_list = undo_list;
|
|
}
|
|
*undo_listp = undo_list;
|
|
return 0;
|
|
}
|
|
|
|
static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid)
|
|
{
|
|
struct sem_undo *un;
|
|
|
|
list_for_each_entry_rcu(un, &ulp->list_proc, list_proc) {
|
|
if (un->semid == semid)
|
|
return un;
|
|
}
|
|
return NULL;
|
|
}
|
|
|
|
static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
|
|
{
|
|
struct sem_undo *un;
|
|
|
|
assert_spin_locked(&ulp->lock);
|
|
|
|
un = __lookup_undo(ulp, semid);
|
|
if (un) {
|
|
list_del_rcu(&un->list_proc);
|
|
list_add_rcu(&un->list_proc, &ulp->list_proc);
|
|
}
|
|
return un;
|
|
}
|
|
|
|
/**
|
|
* find_alloc_undo - lookup (and if not present create) undo array
|
|
* @ns: namespace
|
|
* @semid: semaphore array id
|
|
*
|
|
* The function looks up (and if not present creates) the undo structure.
|
|
* The size of the undo structure depends on the size of the semaphore
|
|
* array, thus the alloc path is not that straightforward.
|
|
* Lifetime-rules: sem_undo is rcu-protected, on success, the function
|
|
* performs a rcu_read_lock().
|
|
*/
|
|
static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
|
|
{
|
|
struct sem_array *sma;
|
|
struct sem_undo_list *ulp;
|
|
struct sem_undo *un, *new;
|
|
int nsems, error;
|
|
|
|
error = get_undo_list(&ulp);
|
|
if (error)
|
|
return ERR_PTR(error);
|
|
|
|
rcu_read_lock();
|
|
spin_lock(&ulp->lock);
|
|
un = lookup_undo(ulp, semid);
|
|
spin_unlock(&ulp->lock);
|
|
if (likely(un != NULL))
|
|
goto out;
|
|
|
|
/* no undo structure around - allocate one. */
|
|
/* step 1: figure out the size of the semaphore array */
|
|
sma = sem_obtain_object_check(ns, semid);
|
|
if (IS_ERR(sma)) {
|
|
rcu_read_unlock();
|
|
return ERR_CAST(sma);
|
|
}
|
|
|
|
nsems = sma->sem_nsems;
|
|
if (!ipc_rcu_getref(sma)) {
|
|
rcu_read_unlock();
|
|
un = ERR_PTR(-EIDRM);
|
|
goto out;
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
/* step 2: allocate new undo structure */
|
|
new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
|
|
if (!new) {
|
|
ipc_rcu_putref(sma, ipc_rcu_free);
|
|
return ERR_PTR(-ENOMEM);
|
|
}
|
|
|
|
/* step 3: Acquire the lock on semaphore array */
|
|
rcu_read_lock();
|
|
sem_lock_and_putref(sma);
|
|
if (!ipc_valid_object(&sma->sem_perm)) {
|
|
sem_unlock(sma, -1);
|
|
rcu_read_unlock();
|
|
kfree(new);
|
|
un = ERR_PTR(-EIDRM);
|
|
goto out;
|
|
}
|
|
spin_lock(&ulp->lock);
|
|
|
|
/*
|
|
* step 4: check for races: did someone else allocate the undo struct?
|
|
*/
|
|
un = lookup_undo(ulp, semid);
|
|
if (un) {
|
|
kfree(new);
|
|
goto success;
|
|
}
|
|
/* step 5: initialize & link new undo structure */
|
|
new->semadj = (short *) &new[1];
|
|
new->ulp = ulp;
|
|
new->semid = semid;
|
|
assert_spin_locked(&ulp->lock);
|
|
list_add_rcu(&new->list_proc, &ulp->list_proc);
|
|
ipc_assert_locked_object(&sma->sem_perm);
|
|
list_add(&new->list_id, &sma->list_id);
|
|
un = new;
|
|
|
|
success:
|
|
spin_unlock(&ulp->lock);
|
|
sem_unlock(sma, -1);
|
|
out:
|
|
return un;
|
|
}
|
|
|
|
|
|
/**
|
|
* get_queue_result - retrieve the result code from sem_queue
|
|
* @q: Pointer to queue structure
|
|
*
|
|
* Retrieve the return code from the pending queue. If IN_WAKEUP is found in
|
|
* q->status, then we must loop until the value is replaced with the final
|
|
* value: This may happen if a task is woken up by an unrelated event (e.g.
|
|
* signal) and in parallel the task is woken up by another task because it got
|
|
* the requested semaphores.
|
|
*
|
|
* The function can be called with or without holding the semaphore spinlock.
|
|
*/
|
|
static int get_queue_result(struct sem_queue *q)
|
|
{
|
|
int error;
|
|
|
|
error = q->status;
|
|
while (unlikely(error == IN_WAKEUP)) {
|
|
cpu_relax();
|
|
error = q->status;
|
|
}
|
|
|
|
return error;
|
|
}
|
|
|
|
SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
|
|
unsigned, nsops, const struct timespec __user *, timeout)
|
|
{
|
|
int error = -EINVAL;
|
|
struct sem_array *sma;
|
|
struct sembuf fast_sops[SEMOPM_FAST];
|
|
struct sembuf *sops = fast_sops, *sop;
|
|
struct sem_undo *un;
|
|
int undos = 0, alter = 0, max, locknum;
|
|
struct sem_queue queue;
|
|
unsigned long jiffies_left = 0;
|
|
struct ipc_namespace *ns;
|
|
struct list_head tasks;
|
|
|
|
ns = current->nsproxy->ipc_ns;
|
|
|
|
if (nsops < 1 || semid < 0)
|
|
return -EINVAL;
|
|
if (nsops > ns->sc_semopm)
|
|
return -E2BIG;
|
|
if (nsops > SEMOPM_FAST) {
|
|
sops = kmalloc(sizeof(*sops)*nsops, GFP_KERNEL);
|
|
if (sops == NULL)
|
|
return -ENOMEM;
|
|
}
|
|
if (copy_from_user(sops, tsops, nsops * sizeof(*tsops))) {
|
|
error = -EFAULT;
|
|
goto out_free;
|
|
}
|
|
if (timeout) {
|
|
struct timespec _timeout;
|
|
if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) {
|
|
error = -EFAULT;
|
|
goto out_free;
|
|
}
|
|
if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 ||
|
|
_timeout.tv_nsec >= 1000000000L) {
|
|
error = -EINVAL;
|
|
goto out_free;
|
|
}
|
|
jiffies_left = timespec_to_jiffies(&_timeout);
|
|
}
|
|
max = 0;
|
|
for (sop = sops; sop < sops + nsops; sop++) {
|
|
if (sop->sem_num >= max)
|
|
max = sop->sem_num;
|
|
if (sop->sem_flg & SEM_UNDO)
|
|
undos = 1;
|
|
if (sop->sem_op != 0)
|
|
alter = 1;
|
|
}
|
|
|
|
INIT_LIST_HEAD(&tasks);
|
|
|
|
if (undos) {
|
|
/* On success, find_alloc_undo takes the rcu_read_lock */
|
|
un = find_alloc_undo(ns, semid);
|
|
if (IS_ERR(un)) {
|
|
error = PTR_ERR(un);
|
|
goto out_free;
|
|
}
|
|
} else {
|
|
un = NULL;
|
|
rcu_read_lock();
|
|
}
|
|
|
|
sma = sem_obtain_object_check(ns, semid);
|
|
if (IS_ERR(sma)) {
|
|
rcu_read_unlock();
|
|
error = PTR_ERR(sma);
|
|
goto out_free;
|
|
}
|
|
|
|
error = -EFBIG;
|
|
if (max >= sma->sem_nsems)
|
|
goto out_rcu_wakeup;
|
|
|
|
error = -EACCES;
|
|
if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO))
|
|
goto out_rcu_wakeup;
|
|
|
|
error = security_sem_semop(sma, sops, nsops, alter);
|
|
if (error)
|
|
goto out_rcu_wakeup;
|
|
|
|
error = -EIDRM;
|
|
locknum = sem_lock(sma, sops, nsops);
|
|
/*
|
|
* We eventually might perform the following check in a lockless
|
|
* fashion, considering ipc_valid_object() locking constraints.
|
|
* If nsops == 1 and there is no contention for sem_perm.lock, then
|
|
* only a per-semaphore lock is held and it's OK to proceed with the
|
|
* check below. More details on the fine grained locking scheme
|
|
* entangled here and why it's RMID race safe on comments at sem_lock()
|
|
*/
|
|
if (!ipc_valid_object(&sma->sem_perm))
|
|
goto out_unlock_free;
|
|
/*
|
|
* semid identifiers are not unique - find_alloc_undo may have
|
|
* allocated an undo structure, it was invalidated by an RMID
|
|
* and now a new array with received the same id. Check and fail.
|
|
* This case can be detected checking un->semid. The existence of
|
|
* "un" itself is guaranteed by rcu.
|
|
*/
|
|
if (un && un->semid == -1)
|
|
goto out_unlock_free;
|
|
|
|
queue.sops = sops;
|
|
queue.nsops = nsops;
|
|
queue.undo = un;
|
|
queue.pid = task_tgid_vnr(current);
|
|
queue.alter = alter;
|
|
|
|
error = perform_atomic_semop(sma, &queue);
|
|
if (error == 0) {
|
|
/* If the operation was successful, then do
|
|
* the required updates.
|
|
*/
|
|
if (alter)
|
|
do_smart_update(sma, sops, nsops, 1, &tasks);
|
|
else
|
|
set_semotime(sma, sops);
|
|
}
|
|
if (error <= 0)
|
|
goto out_unlock_free;
|
|
|
|
/* We need to sleep on this operation, so we put the current
|
|
* task into the pending queue and go to sleep.
|
|
*/
|
|
|
|
if (nsops == 1) {
|
|
struct sem *curr;
|
|
curr = &sma->sem_base[sops->sem_num];
|
|
|
|
if (alter) {
|
|
if (sma->complex_count) {
|
|
list_add_tail(&queue.list,
|
|
&sma->pending_alter);
|
|
} else {
|
|
|
|
list_add_tail(&queue.list,
|
|
&curr->pending_alter);
|
|
}
|
|
} else {
|
|
list_add_tail(&queue.list, &curr->pending_const);
|
|
}
|
|
} else {
|
|
if (!sma->complex_count)
|
|
merge_queues(sma);
|
|
|
|
if (alter)
|
|
list_add_tail(&queue.list, &sma->pending_alter);
|
|
else
|
|
list_add_tail(&queue.list, &sma->pending_const);
|
|
|
|
sma->complex_count++;
|
|
}
|
|
|
|
queue.status = -EINTR;
|
|
queue.sleeper = current;
|
|
|
|
sleep_again:
|
|
__set_current_state(TASK_INTERRUPTIBLE);
|
|
sem_unlock(sma, locknum);
|
|
rcu_read_unlock();
|
|
|
|
if (timeout)
|
|
jiffies_left = schedule_timeout(jiffies_left);
|
|
else
|
|
schedule();
|
|
|
|
error = get_queue_result(&queue);
|
|
|
|
if (error != -EINTR) {
|
|
/* fast path: update_queue already obtained all requested
|
|
* resources.
|
|
* Perform a smp_mb(): User space could assume that semop()
|
|
* is a memory barrier: Without the mb(), the cpu could
|
|
* speculatively read in user space stale data that was
|
|
* overwritten by the previous owner of the semaphore.
|
|
*/
|
|
smp_mb();
|
|
|
|
goto out_free;
|
|
}
|
|
|
|
rcu_read_lock();
|
|
sma = sem_obtain_lock(ns, semid, sops, nsops, &locknum);
|
|
|
|
/*
|
|
* Wait until it's guaranteed that no wakeup_sem_queue_do() is ongoing.
|
|
*/
|
|
error = get_queue_result(&queue);
|
|
|
|
/*
|
|
* Array removed? If yes, leave without sem_unlock().
|
|
*/
|
|
if (IS_ERR(sma)) {
|
|
rcu_read_unlock();
|
|
goto out_free;
|
|
}
|
|
|
|
|
|
/*
|
|
* If queue.status != -EINTR we are woken up by another process.
|
|
* Leave without unlink_queue(), but with sem_unlock().
|
|
*/
|
|
if (error != -EINTR)
|
|
goto out_unlock_free;
|
|
|
|
/*
|
|
* If an interrupt occurred we have to clean up the queue
|
|
*/
|
|
if (timeout && jiffies_left == 0)
|
|
error = -EAGAIN;
|
|
|
|
/*
|
|
* If the wakeup was spurious, just retry
|
|
*/
|
|
if (error == -EINTR && !signal_pending(current))
|
|
goto sleep_again;
|
|
|
|
unlink_queue(sma, &queue);
|
|
|
|
out_unlock_free:
|
|
sem_unlock(sma, locknum);
|
|
out_rcu_wakeup:
|
|
rcu_read_unlock();
|
|
wake_up_sem_queue_do(&tasks);
|
|
out_free:
|
|
if (sops != fast_sops)
|
|
kfree(sops);
|
|
return error;
|
|
}
|
|
|
|
SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,
|
|
unsigned, nsops)
|
|
{
|
|
return sys_semtimedop(semid, tsops, nsops, NULL);
|
|
}
|
|
|
|
/* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
|
|
* parent and child tasks.
|
|
*/
|
|
|
|
int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
|
|
{
|
|
struct sem_undo_list *undo_list;
|
|
int error;
|
|
|
|
if (clone_flags & CLONE_SYSVSEM) {
|
|
error = get_undo_list(&undo_list);
|
|
if (error)
|
|
return error;
|
|
atomic_inc(&undo_list->refcnt);
|
|
tsk->sysvsem.undo_list = undo_list;
|
|
} else
|
|
tsk->sysvsem.undo_list = NULL;
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* add semadj values to semaphores, free undo structures.
|
|
* undo structures are not freed when semaphore arrays are destroyed
|
|
* so some of them may be out of date.
|
|
* IMPLEMENTATION NOTE: There is some confusion over whether the
|
|
* set of adjustments that needs to be done should be done in an atomic
|
|
* manner or not. That is, if we are attempting to decrement the semval
|
|
* should we queue up and wait until we can do so legally?
|
|
* The original implementation attempted to do this (queue and wait).
|
|
* The current implementation does not do so. The POSIX standard
|
|
* and SVID should be consulted to determine what behavior is mandated.
|
|
*/
|
|
void exit_sem(struct task_struct *tsk)
|
|
{
|
|
struct sem_undo_list *ulp;
|
|
|
|
ulp = tsk->sysvsem.undo_list;
|
|
if (!ulp)
|
|
return;
|
|
tsk->sysvsem.undo_list = NULL;
|
|
|
|
if (!atomic_dec_and_test(&ulp->refcnt))
|
|
return;
|
|
|
|
for (;;) {
|
|
struct sem_array *sma;
|
|
struct sem_undo *un;
|
|
struct list_head tasks;
|
|
int semid, i;
|
|
|
|
rcu_read_lock();
|
|
un = list_entry_rcu(ulp->list_proc.next,
|
|
struct sem_undo, list_proc);
|
|
if (&un->list_proc == &ulp->list_proc) {
|
|
/*
|
|
* We must wait for freeary() before freeing this ulp,
|
|
* in case we raced with last sem_undo. There is a small
|
|
* possibility where we exit while freeary() didn't
|
|
* finish unlocking sem_undo_list.
|
|
*/
|
|
spin_unlock_wait(&ulp->lock);
|
|
rcu_read_unlock();
|
|
break;
|
|
}
|
|
spin_lock(&ulp->lock);
|
|
semid = un->semid;
|
|
spin_unlock(&ulp->lock);
|
|
|
|
/* exit_sem raced with IPC_RMID, nothing to do */
|
|
if (semid == -1) {
|
|
rcu_read_unlock();
|
|
continue;
|
|
}
|
|
|
|
sma = sem_obtain_object_check(tsk->nsproxy->ipc_ns, semid);
|
|
/* exit_sem raced with IPC_RMID, nothing to do */
|
|
if (IS_ERR(sma)) {
|
|
rcu_read_unlock();
|
|
continue;
|
|
}
|
|
|
|
sem_lock(sma, NULL, -1);
|
|
/* exit_sem raced with IPC_RMID, nothing to do */
|
|
if (!ipc_valid_object(&sma->sem_perm)) {
|
|
sem_unlock(sma, -1);
|
|
rcu_read_unlock();
|
|
continue;
|
|
}
|
|
un = __lookup_undo(ulp, semid);
|
|
if (un == NULL) {
|
|
/* exit_sem raced with IPC_RMID+semget() that created
|
|
* exactly the same semid. Nothing to do.
|
|
*/
|
|
sem_unlock(sma, -1);
|
|
rcu_read_unlock();
|
|
continue;
|
|
}
|
|
|
|
/* remove un from the linked lists */
|
|
ipc_assert_locked_object(&sma->sem_perm);
|
|
list_del(&un->list_id);
|
|
|
|
/* we are the last process using this ulp, acquiring ulp->lock
|
|
* isn't required. Besides that, we are also protected against
|
|
* IPC_RMID as we hold sma->sem_perm lock now
|
|
*/
|
|
list_del_rcu(&un->list_proc);
|
|
|
|
/* perform adjustments registered in un */
|
|
for (i = 0; i < sma->sem_nsems; i++) {
|
|
struct sem *semaphore = &sma->sem_base[i];
|
|
if (un->semadj[i]) {
|
|
semaphore->semval += un->semadj[i];
|
|
/*
|
|
* Range checks of the new semaphore value,
|
|
* not defined by sus:
|
|
* - Some unices ignore the undo entirely
|
|
* (e.g. HP UX 11i 11.22, Tru64 V5.1)
|
|
* - some cap the value (e.g. FreeBSD caps
|
|
* at 0, but doesn't enforce SEMVMX)
|
|
*
|
|
* Linux caps the semaphore value, both at 0
|
|
* and at SEMVMX.
|
|
*
|
|
* Manfred <manfred@colorfullife.com>
|
|
*/
|
|
if (semaphore->semval < 0)
|
|
semaphore->semval = 0;
|
|
if (semaphore->semval > SEMVMX)
|
|
semaphore->semval = SEMVMX;
|
|
semaphore->sempid = task_tgid_vnr(current);
|
|
}
|
|
}
|
|
/* maybe some queued-up processes were waiting for this */
|
|
INIT_LIST_HEAD(&tasks);
|
|
do_smart_update(sma, NULL, 0, 1, &tasks);
|
|
sem_unlock(sma, -1);
|
|
rcu_read_unlock();
|
|
wake_up_sem_queue_do(&tasks);
|
|
|
|
kfree_rcu(un, rcu);
|
|
}
|
|
kfree(ulp);
|
|
}
|
|
|
|
#ifdef CONFIG_PROC_FS
|
|
static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
|
|
{
|
|
struct user_namespace *user_ns = seq_user_ns(s);
|
|
struct sem_array *sma = it;
|
|
time_t sem_otime;
|
|
|
|
/*
|
|
* The proc interface isn't aware of sem_lock(), it calls
|
|
* ipc_lock_object() directly (in sysvipc_find_ipc).
|
|
* In order to stay compatible with sem_lock(), we must wait until
|
|
* all simple semop() calls have left their critical regions.
|
|
*/
|
|
sem_wait_array(sma);
|
|
|
|
sem_otime = get_semotime(sma);
|
|
|
|
seq_printf(s,
|
|
"%10d %10d %4o %10u %5u %5u %5u %5u %10lu %10lu\n",
|
|
sma->sem_perm.key,
|
|
sma->sem_perm.id,
|
|
sma->sem_perm.mode,
|
|
sma->sem_nsems,
|
|
from_kuid_munged(user_ns, sma->sem_perm.uid),
|
|
from_kgid_munged(user_ns, sma->sem_perm.gid),
|
|
from_kuid_munged(user_ns, sma->sem_perm.cuid),
|
|
from_kgid_munged(user_ns, sma->sem_perm.cgid),
|
|
sem_otime,
|
|
sma->sem_ctime);
|
|
|
|
return 0;
|
|
}
|
|
#endif
|