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| author | Helge Deller <deller@gmx.de> | 2015-05-11 22:01:27 +0200 |
|---|---|---|
| committer | Helge Deller <deller@gmx.de> | 2015-05-12 22:03:44 +0200 |
| commit | d045c77c1a69703143a36169c224429c48b9eecd (patch) | |
| tree | f71e78b7585011274db82483cd95718e11171277 /arch | |
| parent | 5fec97d0e3d93717f1d6a958a03e579078088861 (diff) | |
| download | lwn-d045c77c1a69703143a36169c224429c48b9eecd.tar.gz lwn-d045c77c1a69703143a36169c224429c48b9eecd.zip | |
parisc,metag: Fix crashes due to stack randomization on stack-grows-upwards architectures
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
Cc: stable@vger.kernel.org # v3.16+
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/parisc/include/asm/elf.h | 4 | ||||
| -rw-r--r-- | arch/parisc/kernel/sys_parisc.c | 3 |
2 files changed, 7 insertions, 0 deletions
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); } |