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vm: fix vm_pgoff wrap in stack expansion 

Commit 982134ba62 ("mm: avoid wrapping vm_pgoff in mremap()") fixed
the case of a expanding mapping causing vm_pgoff wrapping when you used
mremap.  But there was another case where we expand mappings hiding in
plain sight: the automatic stack expansion.

This fixes that case too.

This one also found by Robert Święcki, using his nasty system call
fuzzer tool.  Good job.

Reported-and-tested-by: Robert Święcki <robert@swiecki.net>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Linus Torvalds 2011-04-13 08:07:28 -07:00
parent 60d48c1e67
commit a626ca6a65
1 changed files with 8 additions and 5 deletions
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13
mm/mmap.c
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@ -1814,11 +1814,14 @@ static int expand_downwards(struct vm_area_struct *vma,
size = vma->vm_end - address;
grow = (vma->vm_start - address) >> PAGE_SHIFT;
error = acct_stack_growth(vma, size, grow);
if (!error) {
vma->vm_start = address;
vma->vm_pgoff -= grow;
perf_event_mmap(vma);
error = -ENOMEM;
if (grow <= vma->vm_pgoff) {
error = acct_stack_growth(vma, size, grow);
if (!error) {
vma->vm_start = address;
vma->vm_pgoff -= grow;
perf_event_mmap(vma);
}
}
}
vma_unlock_anon_vma(vma);