On 4/18/19 12:37 AM, Kees Cook wrote:
On Wed, Apr 17, 2019 at 12:26 AM Alexandre Ghiti <alex@xxxxxxxx> wrote:
Do not offset mmap base address because of stack randomization if
current task does not want randomization.
Maybe mention that this makes this logic match the existing x86 behavior too?
Ok I will add this in case of a v4.
Signed-off-by: Alexandre Ghiti <alex@xxxxxxxx>
Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
Thanks !
-Kees
---
arch/arm64/mm/mmap.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
index ed4f9915f2b8..ac89686c4af8 100644
--- a/arch/arm64/mm/mmap.c
+++ b/arch/arm64/mm/mmap.c
@@ -65,7 +65,11 @@ unsigned long arch_mmap_rnd(void)
static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack)
{
unsigned long gap = rlim_stack->rlim_cur;
- unsigned long pad = (STACK_RND_MASK << PAGE_SHIFT) + stack_guard_gap;
+ unsigned long pad = stack_guard_gap;
+
+ /* Account for stack randomization if necessary */
+ if (current->flags & PF_RANDOMIZE)
+ pad += (STACK_RND_MASK << PAGE_SHIFT);
/* Values close to RLIM_INFINITY can overflow. */
if (gap + pad > gap)
--
2.20.1
