Patch "mm: fix NULL ptr deref when walking hugepages" has been added to the 3.4-stable tree

This is a note to let you know that I've just added the patch titled

mm: fix NULL ptr deref when walking hugepages

to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
mm-fix-null-ptr-deref-when-walking-hugepages.patch
and it can be found in the queue-3.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Sasha Levin <[email protected]>
Date: Tue, 29 May 2012 15:06:15 -0700
Subject: mm: fix NULL ptr deref when walking hugepages

From: Sasha Levin <[email protected]>

commit 08fa29d916c6e271ad13978cd993e7238c68db97 upstream.

A missing validation of the value returned by find_vma() could cause a NULL ptr dereference when walking the pagetable.

This is triggerable from usermode by a simple user by trying to read a page info out of /proc/pid/pagemap which doesn't exist.

Introduced by commit 025c5b2451e4 ("thp: optimize away unnecessary page table locking").

---
 fs/proc/task_mmu.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -784,7 +784,7 @@ static int pagemap_pte_range(pmd_t *pmd,
 
 	/* find the first VMA at or above 'addr' */
 	vma = find_vma(walk->mm, addr);
-	if (pmd_trans_huge_lock(pmd, vma) == 1) {
+	if (vma && pmd_trans_huge_lock(pmd, vma) == 1) {
 		for (; addr != end; addr += PAGE_SIZE) {
 			unsigned long offset;
 

Patches currently in stable-queue which might be from [email protected] are

queue-3.4/mm-fix-null-ptr-deref-when-walking-hugepages.patch