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23c8cec8cf
There is a permission discrepancy when consulting msq ipc object metadata between /proc/sysvipc/msg (0444) and the MSG_STAT shmctl command. The later does permission checks for the object vs S_IRUGO. As such there can be cases where EACCESS is returned via syscall but the info is displayed anyways in the procfs files. While this might have security implications via info leaking (albeit no writing to the msq metadata), this behavior goes way back and showing all the objects regardless of the permissions was most likely an overlook - so we are stuck with it. Furthermore, modifying either the syscall or the procfs file can cause userspace programs to break (ie ipcs). Some applications require getting the procfs info (without root privileges) and can be rather slow in comparison with a syscall -- up to 500x in some reported cases for shm. This patch introduces a new MSG_STAT_ANY command such that the msq ipc object permissions are ignored, and only audited instead. In addition, I've left the lsm security hook checks in place, as if some policy can block the call, then the user has no other choice than just parsing the procfs file. Link: http://lkml.kernel.org/r/20180215162458.10059-4-dave@stgolabs.net Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Reported-by: Robert Kettler <robert.kettler@outlook.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Kees Cook <keescook@chromium.org> Cc: Manfred Spraul <manfred@colorfullife.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Michal Hocko <mhocko@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
91 lines
3.3 KiB
C
91 lines
3.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
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#ifndef _UAPI_LINUX_MSG_H
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#define _UAPI_LINUX_MSG_H
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#include <linux/ipc.h>
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/* ipcs ctl commands */
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#define MSG_STAT 11
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#define MSG_INFO 12
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#define MSG_STAT_ANY 13
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/* msgrcv options */
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#define MSG_NOERROR 010000 /* no error if message is too big */
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#define MSG_EXCEPT 020000 /* recv any msg except of specified type.*/
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#define MSG_COPY 040000 /* copy (not remove) all queue messages */
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/* Obsolete, used only for backwards compatibility and libc5 compiles */
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struct msqid_ds {
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struct ipc_perm msg_perm;
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struct msg *msg_first; /* first message on queue,unused */
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struct msg *msg_last; /* last message in queue,unused */
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__kernel_time_t msg_stime; /* last msgsnd time */
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__kernel_time_t msg_rtime; /* last msgrcv time */
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__kernel_time_t msg_ctime; /* last change time */
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unsigned long msg_lcbytes; /* Reuse junk fields for 32 bit */
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unsigned long msg_lqbytes; /* ditto */
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unsigned short msg_cbytes; /* current number of bytes on queue */
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unsigned short msg_qnum; /* number of messages in queue */
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unsigned short msg_qbytes; /* max number of bytes on queue */
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__kernel_ipc_pid_t msg_lspid; /* pid of last msgsnd */
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__kernel_ipc_pid_t msg_lrpid; /* last receive pid */
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};
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/* Include the definition of msqid64_ds */
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#include <asm/msgbuf.h>
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/* message buffer for msgsnd and msgrcv calls */
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struct msgbuf {
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__kernel_long_t mtype; /* type of message */
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char mtext[1]; /* message text */
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};
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/* buffer for msgctl calls IPC_INFO, MSG_INFO */
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struct msginfo {
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int msgpool;
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int msgmap;
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int msgmax;
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int msgmnb;
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int msgmni;
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int msgssz;
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int msgtql;
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unsigned short msgseg;
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};
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/*
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* MSGMNI, MSGMAX and MSGMNB are default values which can be
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* modified by sysctl.
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*
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* MSGMNI is the upper limit for the number of messages queues per
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* namespace.
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* It has been chosen to be as large possible without facilitating
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* scenarios where userspace causes overflows when adjusting the limits via
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* operations of the form retrieve current limit; add X; update limit".
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*
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* MSGMNB is the default size of a new message queue. Non-root tasks can
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* decrease the size with msgctl(IPC_SET), root tasks
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* (actually: CAP_SYS_RESOURCE) can both increase and decrease the queue
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* size. The optimal value is application dependent.
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* 16384 is used because it was always used (since 0.99.10)
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*
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* MAXMAX is the maximum size of an individual message, it's a global
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* (per-namespace) limit that applies for all message queues.
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* It's set to 1/2 of MSGMNB, to ensure that at least two messages fit into
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* the queue. This is also an arbitrary choice (since 2.6.0).
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*/
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#define MSGMNI 32000 /* <= IPCMNI */ /* max # of msg queue identifiers */
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#define MSGMAX 8192 /* <= INT_MAX */ /* max size of message (bytes) */
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#define MSGMNB 16384 /* <= INT_MAX */ /* default max size of a message queue */
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/* unused */
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#define MSGPOOL (MSGMNI * MSGMNB / 1024) /* size in kbytes of message pool */
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#define MSGTQL MSGMNB /* number of system message headers */
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#define MSGMAP MSGMNB /* number of entries in message map */
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#define MSGSSZ 16 /* message segment size */
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#define __MSGSEG ((MSGPOOL * 1024) / MSGSSZ) /* max no. of segments */
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#define MSGSEG (__MSGSEG <= 0xffff ? __MSGSEG : 0xffff)
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#endif /* _UAPI_LINUX_MSG_H */
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