[PATCH 3.12 111/146] metag: Reduce maximum stack size to 256MB

Jiri Slaby
2014-06-09T09:27:26Z

From: James Hogan <james.hogan@imgtec.com>

3.12-stable review patch. If anyone has any objections, please let me know.

===============

commit d71f290b4e98a39f49f2595a13be3b4d5ce8e1f1 upstream.

Specify the maximum stack size for arches where the stack grows upward
(parisc and metag) in asm/processor.h rather than hard coding in
fs/exec.c so that metag can specify a smaller value of 256MB rather than
1GB.

This fixes a BUG on metag if the RLIMIT_STACK hard limit is increased
beyond a safe value by root. E.g. when starting a process after running
"ulimit -H -s unlimited" it will then attempt to use a stack size of the
maximum 1GB which is far too big for metag's limited user virtual
address space (stack_top is usually 0x3ffff000):

BUG: failure at fs/exec.c:589/shift_arg_pages()!

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Helge Deller <deller@gmx.de>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: linux-parisc@vger.kernel.org
Cc: linux-metag@vger.kernel.org
Cc: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
arch/metag/include/asm/processor.h | 2 ++
arch/parisc/include/asm/processor.h | 2 ++
fs/exec.c | 6 +++---
3 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/metag/include/asm/processor.h b/arch/metag/include/asm/processor.h
index f16477d1f571..3be8581af495 100644
--- a/arch/metag/include/asm/processor.h
+++ b/arch/metag/include/asm/processor.h
@@ -22,6 +22,8 @@
/* Add an extra page of padding at the top of the stack for the guard page. */
#define STACK_TOP (TASK_SIZE - PAGE_SIZE)
#define STACK_TOP_MAX STACK_TOP
+/* Maximum virtual space for stack */
+#define STACK_SIZE_MAX (1 << 28) /* 256 MB */

/* This decides where the kernel will search for a free chunk of vm
* space during mmap's.
diff --git a/arch/parisc/include/asm/processor.h b/arch/parisc/include/asm/processor.h
index cc2290a3cace..c6ee86542fec 100644
--- a/arch/parisc/include/asm/processor.h
+++ b/arch/parisc/include/asm/processor.h
@@ -53,6 +53,8 @@
#define STACK_TOP TASK_SIZE
#define STACK_TOP_MAX DEFAULT_TASK_SIZE

+#define STACK_SIZE_MAX (1 << 30) /* 1 GB */
+
#endif

#ifndef __ASSEMBLY__
diff --git a/fs/exec.c b/fs/exec.c
index bb8afc1d1df4..95eef54de2b6 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -657,10 +657,10 @@ int setup_arg_pages(struct linux_binprm *bprm,
unsigned long rlim_stack;

#ifdef CONFIG_STACK_GROWSUP
- /* Limit stack size to 1GB */
+ /* Limit stack size */
stack_base = rlimit_max(RLIMIT_STACK);
- if (stack_base > (1 << 30))
- stack_base = 1 << 30;
+ if (stack_base > STACK_SIZE_MAX)
+ stack_base = STACK_SIZE_MAX;

/* Make sure we didn't let the argument array grow too large. */
if (vma->vm_end - vma->vm_start > stack_base)
--
1.9.3