[PATCH AUTOSEL 4.19 33/33] arm: use STACK_TOP when computing mmap base address

Sasha Levin
2019-09-29T17:35:38Z

From: Alexandre Ghiti <alex@ghiti.fr>

[ Upstream commit 86e568e9c0525fc40e76d827212d5e9721cf7504 ]

mmap base address must be computed wrt stack top address, using TASK_SIZE
is wrong since STACK_TOP and TASK_SIZE are not equivalent.

Link: http://lkml.kernel.org/r/20190730055113.23635-8-alex@ghiti.fr
Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: James Hogan <jhogan@kernel.org>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/arm/mm/mmap.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c
index bff3d00bda5be..0b94b674aa91f 100644
--- a/arch/arm/mm/mmap.c
+++ b/arch/arm/mm/mmap.c
@@ -19,7 +19,7 @@

/* gap between mmap and stack */
#define MIN_GAP (128*1024*1024UL)
-#define MAX_GAP ((TASK_SIZE)/6*5)
+#define MAX_GAP ((STACK_TOP)/6*5)
#define STACK_RND_MASK (0x7ff >> (PAGE_SHIFT - 12))

static int mmap_is_legacy(struct rlimit *rlim_stack)
@@ -51,7 +51,7 @@ static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack)
else if (gap > MAX_GAP)
gap = MAX_GAP;

- return PAGE_ALIGN(TASK_SIZE - gap - rnd);
+ return PAGE_ALIGN(STACK_TOP - gap - rnd);
}

/*
--
2.20.1