diff options
| author | Helge Deller <deller@gmx.de> | 2015-05-11 22:01:27 +0200 |
|---|---|---|
| committer | Sasha Levin <sasha.levin@oracle.com> | 2015-06-10 13:42:33 -0400 |
| commit | 6fa3566b04207140b2f61813333baa554f0090af (patch) | |
| tree | d4d403b85515cd123e6e3a800f331e118e86872e /fs | |
| parent | 40b09824118a183f5ab0f6d4161911d505e62ee8 (diff) | |
parisc,metag: Fix crashes due to stack randomization on stack-grows-upwards architectures
[ Upstream commit d045c77c1a69703143a36169c224429c48b9eecd ]
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+
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/exec.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/fs/exec.c b/fs/exec.c index 2e83209016ec..b7a5f46181b0 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -658,6 +658,9 @@ 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; |