mm: fix missing page table unmap for stack guard page failure case

.. 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>

diff --git a/mm/memory.c b/mm/memory.c
index 9606ceb..9b3b73f 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2792,8 +2792,10 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
        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;
+       }
 
        if (!(flags & FAULT_FLAG_WRITE)) {
                entry = pte_mkspecial(pfn_pte(my_zero_pfn(address),