[v6,03/14] arm64: Consider stack randomization for mmap base only when necessary
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Message ID 20190808061756.19712-4-alex@ghiti.fr
State New
Headers show
Series
  • Provide generic top-down mmap layout functions
Related show

Commit Message

Alex Ghiti Aug. 8, 2019, 6:17 a.m. UTC
Do not offset mmap base address because of stack randomization if
current task does not want randomization.
Note that x86 already implements this behaviour.

Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
---
 arch/arm64/mm/mmap.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

Patch
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diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
index bb0140afed66..e4acaead67de 100644
--- a/arch/arm64/mm/mmap.c
+++ b/arch/arm64/mm/mmap.c
@@ -54,7 +54,11 @@  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)