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27ae357fa8
Since exit_mmap() is done without the protection of mm->mmap_sem, it is
possible for the oom reaper to concurrently operate on an mm until
MMF_OOM_SKIP is set.
This allows munlock_vma_pages_all() to concurrently run while the oom
reaper is operating on a vma. Since munlock_vma_pages_range() depends
on clearing VM_LOCKED from vm_flags before actually doing the munlock to
determine if any other vmas are locking the same memory, the check for
VM_LOCKED in the oom reaper is racy.
This is especially noticeable on architectures such as powerpc where
clearing a huge pmd requires serialize_against_pte_lookup(). If the pmd
is zapped by the oom reaper during follow_page_mask() after the check
for pmd_none() is bypassed, this ends up deferencing a NULL ptl or a
kernel oops.
Fix this by manually freeing all possible memory from the mm before
doing the munlock and then setting MMF_OOM_SKIP. The oom reaper can not
run on the mm anymore so the munlock is safe to do in exit_mmap(). It
also matches the logic that the oom reaper currently uses for
determining when to set MMF_OOM_SKIP itself, so there's no new risk of
excessive oom killing.
This issue fixes CVE-2018-1000200.
Link: http://lkml.kernel.org/r/alpine.DEB.2.21.1804241526320.238665@chino.kir.corp.google.com
Fixes: 2129258024 ("mm: oom: let oom_reap_task and exit_mmap run concurrently")
Signed-off-by: David Rientjes <rientjes@google.com>
Suggested-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: <stable@vger.kernel.org> [4.14+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
121 lines
3.1 KiB
C
121 lines
3.1 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __INCLUDE_LINUX_OOM_H
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#define __INCLUDE_LINUX_OOM_H
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#include <linux/sched/signal.h>
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#include <linux/types.h>
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#include <linux/nodemask.h>
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#include <uapi/linux/oom.h>
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#include <linux/sched/coredump.h> /* MMF_* */
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#include <linux/mm.h> /* VM_FAULT* */
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struct zonelist;
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struct notifier_block;
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struct mem_cgroup;
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struct task_struct;
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/*
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* Details of the page allocation that triggered the oom killer that are used to
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* determine what should be killed.
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*/
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struct oom_control {
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/* Used to determine cpuset */
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struct zonelist *zonelist;
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/* Used to determine mempolicy */
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nodemask_t *nodemask;
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/* Memory cgroup in which oom is invoked, or NULL for global oom */
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struct mem_cgroup *memcg;
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/* Used to determine cpuset and node locality requirement */
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const gfp_t gfp_mask;
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/*
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* order == -1 means the oom kill is required by sysrq, otherwise only
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* for display purposes.
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*/
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const int order;
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/* Used by oom implementation, do not set */
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unsigned long totalpages;
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struct task_struct *chosen;
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unsigned long chosen_points;
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};
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extern struct mutex oom_lock;
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static inline void set_current_oom_origin(void)
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{
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current->signal->oom_flag_origin = true;
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}
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static inline void clear_current_oom_origin(void)
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{
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current->signal->oom_flag_origin = false;
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}
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static inline bool oom_task_origin(const struct task_struct *p)
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{
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return p->signal->oom_flag_origin;
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}
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static inline bool tsk_is_oom_victim(struct task_struct * tsk)
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{
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return tsk->signal->oom_mm;
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}
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/*
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* Use this helper if tsk->mm != mm and the victim mm needs a special
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* handling. This is guaranteed to stay true after once set.
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*/
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static inline bool mm_is_oom_victim(struct mm_struct *mm)
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{
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return test_bit(MMF_OOM_VICTIM, &mm->flags);
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}
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/*
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* Checks whether a page fault on the given mm is still reliable.
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* This is no longer true if the oom reaper started to reap the
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* address space which is reflected by MMF_UNSTABLE flag set in
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* the mm. At that moment any !shared mapping would lose the content
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* and could cause a memory corruption (zero pages instead of the
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* original content).
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*
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* User should call this before establishing a page table entry for
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* a !shared mapping and under the proper page table lock.
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*
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* Return 0 when the PF is safe VM_FAULT_SIGBUS otherwise.
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*/
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static inline int check_stable_address_space(struct mm_struct *mm)
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{
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if (unlikely(test_bit(MMF_UNSTABLE, &mm->flags)))
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return VM_FAULT_SIGBUS;
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return 0;
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}
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void __oom_reap_task_mm(struct mm_struct *mm);
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extern unsigned long oom_badness(struct task_struct *p,
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struct mem_cgroup *memcg, const nodemask_t *nodemask,
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unsigned long totalpages);
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extern bool out_of_memory(struct oom_control *oc);
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extern void exit_oom_victim(void);
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extern int register_oom_notifier(struct notifier_block *nb);
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extern int unregister_oom_notifier(struct notifier_block *nb);
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extern bool oom_killer_disable(signed long timeout);
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extern void oom_killer_enable(void);
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extern struct task_struct *find_lock_task_mm(struct task_struct *p);
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/* sysctls */
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extern int sysctl_oom_dump_tasks;
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extern int sysctl_oom_kill_allocating_task;
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extern int sysctl_panic_on_oom;
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#endif /* _INCLUDE_LINUX_OOM_H */
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