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Commit f91a9c65 authored by Alexandre Ghiti's avatar Alexandre Ghiti Committed by Greg Kroah-Hartman
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arm: properly account for stack randomization and stack guard gap 

[ 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/20170622200033.25714-1-riel@redhat.com

Link: http://lkml.kernel.org/r/20190730055113.23635-7-alex@ghiti.fr


Signed-off-by: default avatarAlexandre Ghiti <alex@ghiti.fr>
Acked-by: default avatarKees Cook <keescook@chromium.org>
Reviewed-by: default avatarLuis 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 53ba8d43

arch/arm/mm/mmap.c

+12 −2
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ 
/* gap between mmap and stack */

#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;