mm: fix page table unmap for stack guard page properly

[net-next-2.6.git] / mm / memory.c

diff --git a/mm/memory.c b/mm/memory.c
index 9b3b73f4ae9c77350abd052abbdc889634258801..b6e5fd23cc5a48e13f49b0d824ca3cc9713bd3ab 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2792,24 +2792,23 @@ 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) {
-               pte_unmap(page_table);
+       pte_unmap(page_table);
+
+       /* Check if we need to add a guard page to the stack */
+       if (check_stack_guard_page(vma, address) < 0)
                return VM_FAULT_SIGBUS;
-       }
 
+       /* Use the zero-page for reads */
        if (!(flags & FAULT_FLAG_WRITE)) {
                entry = pte_mkspecial(pfn_pte(my_zero_pfn(address),
                                                vma->vm_page_prot));
-               ptl = pte_lockptr(mm, pmd);
-               spin_lock(ptl);
+               page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
                if (!pte_none(*page_table))
                        goto unlock;
                goto setpte;
        }
 
        /* Allocate our own private page. */
-       pte_unmap(page_table);
-
        if (unlikely(anon_vma_prepare(vma)))
                goto oom;
        page = alloc_zeroed_user_highpage_movable(vma, address);