1 files changed, 22 insertions, 8 deletions

diff --git a/mm/memory.c b/mm/memory.c
index b6e5fd23cc5..6b2ab105185 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2760,21 +2760,35 @@ out_release:
 }
 
 /*
- * This is like a special single-page "expand_downwards()",
- * except we must first make sure that 'address-PAGE_SIZE'
+ * This is like a special single-page "expand_{down|up}wards()",
+ * except we must first make sure that 'address{-|+}PAGE_SIZE'
  * doesn't hit another vma.
- *
- * The "find_vma()" will do the right thing even if we wrap
  */
 static inline int check_stack_guard_page(struct vm_area_struct *vma, unsigned long address)
 {
         address &= PAGE_MASK;
         if ((vma->vm_flags & VM_GROWSDOWN) && address == vma->vm_start) {
-                address -= PAGE_SIZE;
-                if (find_vma(vma->vm_mm, address) != vma)
-                        return -ENOMEM;
+                struct vm_area_struct *prev = vma->vm_prev;
+
+                /*
+                 * Is there a mapping abutting this one below?
+                 *
+                 * That's only ok if it's the same stack mapping
+                 * that has gotten split..
+                 */
+                if (prev && prev->vm_end == address)
+                        return prev->vm_flags & VM_GROWSDOWN ? 0 : -ENOMEM;
+
+                expand_stack(vma, address - PAGE_SIZE);
+        }
+        if ((vma->vm_flags & VM_GROWSUP) && address + PAGE_SIZE == vma->vm_end) {
+                struct vm_area_struct *next = vma->vm_next;
+
+                /* As VM_GROWSDOWN but s/below/above/ */
+                if (next && next->vm_start == address + PAGE_SIZE)
+                        return next->vm_flags & VM_GROWSUP ? 0 : -ENOMEM;
 
-                expand_stack(vma, address);
+                expand_upwards(vma, address + PAGE_SIZE);
         }
         return 0;
 }