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mm: check for no mmaps in exit_mmap()

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When dup_mmap() ooms we can end up with mm->mmap == NULL.  The error
path does mmput() and unmap_vmas() gets a NULL vma which it
dereferences.

In exit_mmap() there is nothing to do at all for this case, we can
cancel the callpath right there.

[akpm@linux-foundation.org: add sorely-needed comment]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Johannes Weiner 2009-01-06 14:40:31 -08:00 committed by Linus Torvalds
parent 084f71ae5c
commit dcd4a049b9
1 changed files with 3 additions and 0 deletions
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3
mm/mmap.c
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@ -2090,6 +2090,9 @@ void exit_mmap(struct mm_struct *mm)
arch_exit_mmap(mm);
mmu_notifier_release(mm);
if (!mm->mmap) /* Can happen if dup_mmap() received an OOM */
return;
if (mm->locked_vm) {
vma = mm->mmap;
while (vma) {