From 435ad8041adc50009defb16b2bfd75f797fb323d Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Tue, 12 Nov 2013 15:07:55 -0800 Subject: [PATCH] s390/mmap: randomize mmap base for bottom up direction Implement mmap base randomization for the bottom up direction, so ASLR works for both mmap layouts on s390. See also commit 1fc2757e4e8f ("x86 get_unmapped_area(): use proper mmap base for bottom-up direction"). Signed-off-by: Heiko Carstens Cc: Radu Caragea Cc: Michel Lespinasse Cc: Catalin Marinas Cc: Will Deacon Cc: Chris Metcalf Cc: Martin Schwidefsky Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- 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 6bcb045d2bd2f..9b436c21195ec 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(); @@ -164,7 +169,7 @@ 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(); -- 2.39.5