[34-longterm 149/260] guard page for stacks that grow upwards

Paul Gortmaker
2011-01-02T07:43:33Z

From: Luck, Tony <tony.luck@intel.com>

commit 8ca3eb08097f6839b2206e2242db4179aee3cfb3 upstream.

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>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
include/linux/mm.h | 8 +++++++-
mm/memory.c | 15 +++++++++++----
mm/mmap.c | 3 ---
3 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 462acaf..04fb7f6 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -78,7 +78,11 @@ extern unsigned int kobjsize(const void *objp);
#define VM_MAYSHARE 0x00000080

#define VM_GROWSDOWN 0x00000100 /* general info on the segment */
+#if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64)
#define VM_GROWSUP 0x00000200
+#else
+#define VM_GROWSUP 0x00000000
+#endif
#define VM_PFNMAP 0x00000400 /* Page-ranges managed without "struct page", just pure PFN */
#define VM_DENYWRITE 0x00000800 /* ETXTBSY on write attempts.. */

@@ -1325,8 +1329,10 @@ unsigned long ra_submit(struct file_ra_state *ra,

/* Do stack extension */
extern int expand_stack(struct vm_area_struct *vma, unsigned long address);
-#ifdef CONFIG_IA64
+#if VM_GROWSUP
extern int expand_upwards(struct vm_area_struct *vma, unsigned long address);
+#else
+ #define expand_upwards(vma, address) do { } while (0)
#endif
extern int expand_stack_downwards(struct vm_area_struct *vma,
unsigned long address);
diff --git a/mm/memory.c b/mm/memory.c
index 47fb0a0..3410236 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2751,11 +2751,9 @@ 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)
{
@@ -2774,6 +2772,15 @@ 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 3867cfc..10cb197 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1704,9 +1704,6 @@ 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;
--
1.7.3.3