From: Alexandre Ghiti <alex@xxxxxxxx> Subject: arm64: consider stack randomization for mmap base only when necessary Do not offset mmap base address because of stack randomization if current task does not want randomization. Note that x86 already implements this behaviour. Link: http://lkml.kernel.org/r/20190730055113.23635-4-alex@xxxxxxxx Signed-off-by: Alexandre Ghiti <alex@xxxxxxxx> Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx> Acked-by: Kees Cook <keescook@xxxxxxxxxxxx> Reviewed-by: Christoph Hellwig <hch@xxxxxx> Reviewed-by: Luis Chamberlain <mcgrof@xxxxxxxxxx> Cc: Albert Ou <aou@xxxxxxxxxxxxxxxxx> Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx> Cc: James Hogan <jhogan@xxxxxxxxxx> Cc: Palmer Dabbelt <palmer@xxxxxxxxxx> Cc: Paul Burton <paul.burton@xxxxxxxx> Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx> Cc: Russell King <linux@xxxxxxxxxxxxxxx> Cc: Will Deacon <will.deacon@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- arch/arm64/mm/mmap.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) --- a/arch/arm64/mm/mmap.c~arm64-consider-stack-randomization-for-mmap-base-only-when-necessary +++ a/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) _
