From patchwork Tue Oct 11 15:39:20 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Subject: [2/3] vm: fix vm_pgoff wrap in stack expansion - CVE-2011-2496 Date: Tue, 11 Oct 2011 05:39:20 -0000 From: Paolo Pisati X-Patchwork-Id: 118999 Message-Id: <1318347561-1410-3-git-send-email-paolo.pisati@canonical.com> To: kernel-team@lists.ubuntu.com From: Linus Torvalds vm: fix vm_pgoff wrap in stack expansion 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 Cc: stable@kernel.org Signed-off-by: Linus Torvalds CVE-2011-2496 BugLink: http://bugs.launchpad.net/bugs/869243 commit upstream a626ca6a656450e9f4df91d0dda238fff23285f4 Signed-off-by: Paolo Pisati --- mm/mmap.c | 11 +++++++---- 1 files changed, 7 insertions(+), 4 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index a53ad79..1508d86 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1779,10 +1779,13 @@ 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);