From: Alexandre Ghiti <[email protected]> [ Upstream commit af0f4297286f13a75edf93677b1fb2fc16c412a7 ]
This commit takes care of stack randomization and stack guard gap when computing mmap base address and checks if the task asked for randomization. This fixes the problem uncovered and not fixed for arm here: https://lkml.kernel.org/r/[email protected] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Alexandre Ghiti <[email protected]> Acked-by: Kees Cook <[email protected]> Reviewed-by: Luis Chamberlain <[email protected]> Cc: Albert Ou <[email protected]> Cc: Alexander Viro <[email protected]> Cc: Catalin Marinas <[email protected]> Cc: Christoph Hellwig <[email protected]> Cc: Christoph Hellwig <[email protected]> Cc: James Hogan <[email protected]> Cc: Palmer Dabbelt <[email protected]> Cc: Paul Burton <[email protected]> Cc: Ralf Baechle <[email protected]> Cc: Russell King <[email protected]> Cc: Will Deacon <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Sasha Levin <[email protected]> --- arch/arm/mm/mmap.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c index f866870db749c..bff3d00bda5be 100644 --- a/arch/arm/mm/mmap.c +++ b/arch/arm/mm/mmap.c @@ -18,8 +18,9 @@ (((pgoff)<<PAGE_SHIFT) & (SHMLBA-1))) /* gap between mmap and stack */ -#define MIN_GAP (128*1024*1024UL) -#define MAX_GAP ((TASK_SIZE)/6*5) +#define MIN_GAP (128*1024*1024UL) +#define MAX_GAP ((TASK_SIZE)/6*5) +#define STACK_RND_MASK (0x7ff >> (PAGE_SHIFT - 12)) static int mmap_is_legacy(struct rlimit *rlim_stack) { @@ -35,6 +36,15 @@ static int mmap_is_legacy(struct rlimit *rlim_stack) static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack) { unsigned long gap = rlim_stack->rlim_cur; + 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) + gap += pad; if (gap < MIN_GAP) gap = MIN_GAP; -- 2.20.1
