guard page for stacks that grow upwards

pa-risc and ia64 have stacks that grow upwards. Check that
they do not run into other mappings. By making VM_GROWSUP
0x0 on architectures that do not ever use it, we can avoid
some unpleasant #ifdefs in check_stack_guard_page().

Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 11 insertions, 4 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 2ed2267439df..6b2ab1051851 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2760,11 +2760,9 @@ 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)
 {
@@ -2783,6 +2781,15 @@ static inline int check_stack_guard_page(struct vm_area_struct *vma, unsigned lo
 
                 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_upwards(vma, address + PAGE_SIZE);
+        }
         return 0;
 }