From a626ca6a656450e9f4df91d0dda238fff23285f4 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Wed, 13 Apr 2011 08:07:28 -0700 Subject: vm: fix vm_pgoff wrap in stack expansion MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Linus Torvalds 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 Święcki, using his nasty system call fuzzer tool. Good job. Reported-and-tested-by: Robert Święcki Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/mmap.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1814,10 +1814,13 @@ 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; + } } } vma_unlock_anon_vma(vma);