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Date: Tue, 24 Aug 2010 09:31:41 -0700
From: "Luck, Tony" <tony.luck@...el.com>
To: "Linus Torvalds" <torvalds@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, linux-parisc@...r.kernel.org,
linux-ia64@...r.kernel.org
Subject: [PATCH] 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.
Signed-off-by: Tony Luck <tony.luck@...el.com>
---
Updated to match the new code - still not tested on pa-risc.
The #ifdefs are ugly - suggestions welcome on how to make
the code prettier.
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 709f672..089d135 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1330,7 +1330,7 @@ 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 defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64)
extern int expand_upwards(struct vm_area_struct *vma, unsigned long address);
#endif
extern int expand_stack_downwards(struct vm_area_struct *vma,
diff --git a/mm/memory.c b/mm/memory.c
index 2ed2267..5127b1c 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2760,29 +2760,43 @@ 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) {
- struct vm_area_struct *prev = vma->vm_prev;
+ if (vma->vm_flags & VM_GROWSDOWN) {
+ address &= PAGE_MASK;
+ if (address == vma->vm_start) {
+ 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;
+ /*
+ * 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);
+ expand_stack(vma, address - PAGE_SIZE);
+ }
+ }
+#if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64)
+ else if (vma->vm_flags & VM_GROWSUP) {
+ address = PAGE_ALIGN(address + 1);
+ if (address == vma->vm_end) {
+ struct vm_area_struct *next = vma->vm_next;
+
+ /* As VM_GROWSDOWN but s/below/above/ */
+ if (next && next->vm_start == address)
+ return next->vm_flags & VM_GROWSUP ? 0 : -ENOMEM;
+
+ expand_upwards(vma, address);
+ }
}
+#endif
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;
--
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