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authorDavid Rientjes <rientjes@google.com>2018-05-12 02:02:04 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2018-05-12 03:28:45 +0300
commit27ae357fa82be5ab73b2ef8d39dcb8ca2563483a (patch)
tree78596e2b24c4923f8d17152ac23b15d2d7681c19 /include/linux/oom.h
parent013567be19761e2d14fc2a2676fe7686ac54c9ac (diff)
downloadlinux-27ae357fa82be5ab73b2ef8d39dcb8ca2563483a.tar.xz
mm, oom: fix concurrent munlock and oom reaper unmap, v3
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: 212925802454 ("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>
Diffstat (limited to 'include/linux/oom.h')
-rw-r--r--include/linux/oom.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/oom.h b/include/linux/oom.h
index 5bad038ac012..6adac113e96d 100644
--- a/include/linux/oom.h
+++ b/include/linux/oom.h
@@ -95,6 +95,8 @@ static inline int check_stable_address_space(struct mm_struct *mm)
return 0;
}
+void __oom_reap_task_mm(struct mm_struct *mm);
+
extern unsigned long oom_badness(struct task_struct *p,
struct mem_cgroup *memcg, const nodemask_t *nodemask,
unsigned long totalpages);