[2/6] mm: fix missing page table unmap for stack guard page failure case

[Greg KH <gregkh@suse.de>]

2.6.27-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Linus Torvalds <torvalds@linux-foundation.org>

commit 5528f9132cf65d4d892bcbc5684c61e7822b21e9 upstream.

.. which didn't show up in my tests because it's a no-op on x86-64 and
most other architectures.  But we enter the function with the last-level
page table mapped, and should unmap it at exit.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 mm/memory.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2428,8 +2428,10 @@ static int do_anonymous_page(struct mm_s
 	spinlock_t *ptl;
 	pte_t entry;
 
-	if (check_stack_guard_page(vma, address) < 0)
+	if (check_stack_guard_page(vma, address) < 0) {
+		pte_unmap(page_table);
 		return VM_FAULT_SIGBUS;
+	}
 
 	/* Allocate our own private page. */
 	pte_unmap(page_table);