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>

2 files changed, 11 insertions, 7 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 2ed2267..6b2ab10 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;
 }
 
diff --git a/mm/mmap.c b/mm/mmap.c
index 331e51a..6128dc8 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1716,9 +1716,6 @@ static int acct_stack_growth(struct vm_area_struct *vma, unsigned long size, uns
  * PA-RISC uses this for its stack; IA64 for its Register Backing Store.
  * vma is the last one with address > vma->vm_end.  Have to extend vma.
  */
-#ifndef CONFIG_IA64
-static
-#endif
 int expand_upwards(struct vm_area_struct *vma, unsigned long address)
 {
 	int error;