* [PATCH 3.16.y-ckt 039/110] parisc, metag: Fix crashes due to stack randomization on stack-grows-upwards architectures
[not found] <1433512713-22984-1-git-send-email-luis.henriques@canonical.com>
@ 2015-06-05 13:57 ` Luis Henriques
0 siblings, 0 replies; only message in thread
From: Luis Henriques @ 2015-06-05 13:57 UTC (permalink / raw
To: linux-kernel, stable, kernel-team
Cc: Helge Deller, James Hogan, linux-metag, linux-parisc
3.16.7-ckt13 -stable review patch. If anyone has any objections, please let me know.
------------------
From: Helge Deller <deller@gmx.de>
commit d045c77c1a69703143a36169c224429c48b9eecd upstream.
On architectures where the stack grows upwards (CONFIG_STACK_GROWSUP=y,
currently parisc and metag only) stack randomization sometimes leads to crashes
when the stack ulimit is set to lower values than STACK_RND_MASK (which is 8 MB
by default if not defined in arch-specific headers).
The problem is, that when the stack vm_area_struct is set up in fs/exec.c, the
additional space needed for the stack randomization (as defined by the value of
STACK_RND_MASK) was not taken into account yet and as such, when the stack
randomization code added a random offset to the stack start, the stack
effectively got smaller than what the user defined via rlimit_max(RLIMIT_STACK)
which then sometimes leads to out-of-stack situations and crashes.
This patch fixes it by adding the maximum possible amount of memory (based on
STACK_RND_MASK) which theoretically could be added by the stack randomization
code to the initial stack size. That way, the user-defined stack size is always
guaranteed to be at minimum what is defined via rlimit_max(RLIMIT_STACK).
This bug is currently not visible on the metag architecture, because on metag
STACK_RND_MASK is defined to 0 which effectively disables stack randomization.
The changes to fs/exec.c are inside an "#ifdef CONFIG_STACK_GROWSUP"
section, so it does not affect other platformws beside those where the
stack grows upwards (parisc and metag).
Signed-off-by: Helge Deller <deller@gmx.de>
Cc: linux-parisc@vger.kernel.org
Cc: James Hogan <james.hogan@imgtec.com>
Cc: linux-metag@vger.kernel.org
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
arch/parisc/include/asm/elf.h | 4 ++++
arch/parisc/kernel/sys_parisc.c | 3 +++
fs/exec.c | 3 +++
3 files changed, 10 insertions(+)
diff --git a/arch/parisc/include/asm/elf.h b/arch/parisc/include/asm/elf.h
index 3391d061eccc..78c9fd32c554 100644
--- a/arch/parisc/include/asm/elf.h
+++ b/arch/parisc/include/asm/elf.h
@@ -348,6 +348,10 @@ struct pt_regs; /* forward declaration... */
#define ELF_HWCAP 0
+#define STACK_RND_MASK (is_32bit_task() ? \
+ 0x7ff >> (PAGE_SHIFT - 12) : \
+ 0x3ffff >> (PAGE_SHIFT - 12))
+
struct mm_struct;
extern unsigned long arch_randomize_brk(struct mm_struct *);
#define arch_randomize_brk arch_randomize_brk
diff --git a/arch/parisc/kernel/sys_parisc.c b/arch/parisc/kernel/sys_parisc.c
index e1ffea2f9a0b..5aba01ac457f 100644
--- a/arch/parisc/kernel/sys_parisc.c
+++ b/arch/parisc/kernel/sys_parisc.c
@@ -77,6 +77,9 @@ static unsigned long mmap_upper_limit(void)
if (stack_base > STACK_SIZE_MAX)
stack_base = STACK_SIZE_MAX;
+ /* Add space for stack randomization. */
+ stack_base += (STACK_RND_MASK << PAGE_SHIFT);
+
return PAGE_ALIGN(STACK_TOP - stack_base);
}
diff --git a/fs/exec.c b/fs/exec.c
index 68a0843250c9..993ed0aba99a 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -662,6 +662,9 @@ int setup_arg_pages(struct linux_binprm *bprm,
if (stack_base > STACK_SIZE_MAX)
stack_base = STACK_SIZE_MAX;
+ /* Add space for stack randomization. */
+ stack_base += (STACK_RND_MASK << PAGE_SHIFT);
+
/* Make sure we didn't let the argument array grow too large. */
if (vma->vm_end - vma->vm_start > stack_base)
return -ENOMEM;
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2015-06-05 13:57 ` [PATCH 3.16.y-ckt 039/110] parisc, metag: Fix crashes due to stack randomization on stack-grows-upwards architectures Luis Henriques
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