From: Linus Torvalds Date: Wed, 13 Apr 2011 15:07:28 +0000 (-0700) Subject: vm: fix vm_pgoff wrap in stack expansion X-Git-Tag: v2.6.33.20~8 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a2e441bdc3e86699fe95dcf3d54fc83c91d5cd9e;p=thirdparty%2Fkernel%2Fstable.git vm: fix vm_pgoff wrap in stack expansion 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 --- diff --git a/mm/mmap.c b/mm/mmap.c index 892b7d3a9dee8..3e2f805c964e7 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1721,10 +1721,13 @@ 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; + 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);