path: root/fs
diff options
authorHelge Deller <>2015-05-11 22:01:27 +0200
committerHelge Deller <>2015-05-12 22:03:44 +0200
commitd045c77c1a69703143a36169c224429c48b9eecd (patch)
treef71e78b7585011274db82483cd95718e11171277 /fs
parent5fec97d0e3d93717f1d6a958a03e579078088861 (diff)
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 <> Cc: Cc: James Hogan <> Cc: Cc: # v3.16+
Diffstat (limited to 'fs')
1 files changed, 3 insertions, 0 deletions
diff --git a/fs/exec.c b/fs/exec.c
index 49a1c61433b7..1977c2a553ac 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -659,6 +659,9 @@ 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;