Implement mmap base randomization for the bottom up direction, so ASLR works
for both mmap layouts on s390.
See also df54d6fa54 "x86 get_unmapped_area(): use proper mmap base for
bottom-up direction".
Signed-off-by: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
---
arch/s390/mm/mmap.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/arch/s390/mm/mmap.c b/arch/s390/mm/mmap.c
index 4002329..7110c0f 100644
--- a/arch/s390/mm/mmap.c
+++ b/arch/s390/mm/mmap.c
@@ -64,6 +64,11 @@ static unsigned long mmap_rnd(void)
return (get_random_int() & 0x7ffUL) << PAGE_SHIFT;
}
+static unsigned long mmap_base_legacy(void)
+{
+ return TASK_UNMAPPED_BASE + mmap_rnd();
+}
+
static inline unsigned long mmap_base(void)
{
unsigned long gap = rlimit(RLIMIT_STACK);
@@ -89,7 +94,7 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
* bit is set, or if the expected stack growth is unlimited:
*/
if (mmap_is_legacy()) {
- mm->mmap_base = TASK_UNMAPPED_BASE;
+ mm->mmap_base = mmap_base_legacy();
mm->get_unmapped_area = arch_get_unmapped_area;
} else {
mm->mmap_base = mmap_base();
@@ -172,7 +177,7 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
* bit is set, or if the expected stack growth is unlimited:
*/
if (mmap_is_legacy()) {
- mm->mmap_base = TASK_UNMAPPED_BASE;
+ mm->mmap_base = mmap_base_legacy();
mm->get_unmapped_area = s390_get_unmapped_area;
} else {
mm->mmap_base = mmap_base();
--
1.8.3.4
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