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From 68785afca6b04411df86323dca372f136e225639 Mon Sep 17 00:00:00 2001
From: Helge Deller <deller@gmx.de>
Date: Mon, 19 Jun 2017 17:34:05 +0200
Subject: [PATCH 3/3] [SEC][Backport] Allow stack to grow up to address space
limit
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
commit bd726c90b6b8ce87602208701b208a208e6d5600 upstream.
Fix expand_upwards() on architectures with an upward-growing stack (parisc,
metag and partly IA-64) to allow the stack to reliably grow exactly up to
the address space limit given by TASK_SIZE.
Signed-off-by: Helge Deller <deller@gmx.de>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Jan-Simon Möller <jsmoeller@linuxfoundation.org>
---
mm/mmap.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/mm/mmap.c b/mm/mmap.c
index 4a113e3..16aeffc 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2129,16 +2129,19 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address)
if (!(vma->vm_flags & VM_GROWSUP))
return -EFAULT;
- /* Guard against wrapping around to address 0. */
+ /* Guard against exceeding limits of the address space. */
address &= PAGE_MASK;
- address += PAGE_SIZE;
- if (!address)
+ if (address >= TASK_SIZE)
return -ENOMEM;
+ address += PAGE_SIZE;
/* Enforce stack_guard_gap */
gap_addr = address + stack_guard_gap;
- if (gap_addr < address)
- return -ENOMEM;
+
+ /* Guard against overflow */
+ if (gap_addr < address || gap_addr > TASK_SIZE)
+ gap_addr = TASK_SIZE;
+
next = vma->vm_next;
if (next && next->vm_start < gap_addr) {
if (!(next->vm_flags & VM_GROWSUP))
--
2.1.4
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