From a626ca6a656450e9f4df91d0dda238fff23285f4 Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Wed, 13 Apr 2011 08:07:28 -0700
Subject: [PATCH] vm: fix vm_pgoff wrap in stack expansion
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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 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>
---
mm/mmap.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/mm/mmap.c b/mm/mmap.c
index 2ec8eb5a9cdd0..8c05e5b43b69c 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -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);
--
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