[097/101] vm: fix vm_pgoff wrap in stack expansion
From: Greg KH
Date: Wed Nov 02 2011 - 21:46:39 EST
2.6.33-longterm review patch. If anyone has any objections, please let us know.
------------------
From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
commit a626ca6a656450e9f4df91d0dda238fff23285f4 upstream.
Commit 982134ba6261 ("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 Å?wiÄ?cki, using his nasty system call
fuzzer tool. Good job.
Reported-and-tested-by: Robert Å?wiÄ?cki <robert@xxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
---
mm/mmap.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1721,10 +1721,13 @@ static int expand_downwards(struct vm_ar
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;
+ error = -ENOMEM;
+ if (grow <= vma->vm_pgoff) {
+ error = acct_stack_growth(vma, size, grow);
+ if (!error) {
+ vma->vm_start = address;
+ vma->vm_pgoff -= grow;
+ }
}
}
anon_vma_unlock(vma);
--
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