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Subject[patch 57/73] security: protect from stack expantion into low vm addresses
2.6.23-stable review patch.  If anyone has any objections, please let us know.
------------------
From: Eric Paris <eparis@redhat.com>

patch 8869477a49c3e99def1fcdadd6bbc407fea14b45 in mainline.

Add security checks to make sure we are not attempting to expand the
stack into memory protected by mmap_min_addr

Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
mm/mmap.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1619,6 +1619,12 @@ static inline int expand_downwards(struc
*/
if (unlikely(anon_vma_prepare(vma)))
return -ENOMEM;
+
+ address &= PAGE_MASK;
+ error = security_file_mmap(0, 0, 0, 0, address, 1);
+ if (error)
+ return error;
+
anon_vma_lock(vma);

/*
@@ -1626,8 +1632,6 @@ static inline int expand_downwards(struc
* is required to hold the mmap_sem in read mode. We need the
* anon_vma lock to serialize against concurrent expand_stacks.
*/
- address &= PAGE_MASK;
- error = 0;

/* Somebody else might have raced and expanded it already */
if (address < vma->vm_start) {
--


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