path: root/arch/arm64/mm
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authorRik van Riel <riel@redhat.com>2017-07-12 14:36:36 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-07-12 16:26:03 -0700
commitcf92251dc52d2dfae6c6adaeae8b12ea50686946 (patch)
tree31070eeb51cf64d65fec176e546d4fb89b4ec551 /arch/arm64/mm
parentx86/mmap: properly account for stack randomization in mmap_base (diff)
arm64/mmap: properly account for stack randomization in mmap_base
When RLIMIT_STACK is, for example, 256MB, the current code results in a gap between the top of the task and mmap_base of 256MB, failing to take into account the amount by which the stack address was randomized. In other words, the stack gets less than RLIMIT_STACK space. Ensure that the gap between the stack and mmap_base always takes stack randomization and the stack guard gap into account. Obtained from Daniel Micay's linux-hardened tree. Link: http://lkml.kernel.org/r/20170622200033.25714-3-riel@redhat.com Signed-off-by: Daniel Micay <danielmicay@gmail.com> Signed-off-by: Rik van Riel <riel@redhat.com> Reported-by: Florian Weimer <fweimer@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Will Deacon <will.deacon@arm.com> Cc: Daniel Micay <danielmicay@gmail.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Hugh Dickins <hughd@google.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/arm64/mm')
1 files changed, 6 insertions, 1 deletions
diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
index adc208c2ae9c..decccffb03ca 100644
--- a/arch/arm64/mm/mmap.c
+++ b/arch/arm64/mm/mmap.c
@@ -35,7 +35,7 @@
* Leave enough space between the mmap area and the stack to honour ulimit in
* the face of randomisation.
-#define MIN_GAP (SZ_128M + ((STACK_RND_MASK << PAGE_SHIFT) + 1))
+#define MIN_GAP (SZ_128M)
#define MAX_GAP (STACK_TOP/6*5)
static int mmap_is_legacy(void)
@@ -65,6 +65,11 @@ unsigned long arch_mmap_rnd(void)
static unsigned long mmap_base(unsigned long rnd)
unsigned long gap = rlimit(RLIMIT_STACK);
+ unsigned long pad = (STACK_RND_MASK << PAGE_SHIFT) + stack_guard_gap;
+ /* Values close to RLIM_INFINITY can overflow. */
+ if (gap + pad > gap)
+ gap += pad;
if (gap < MIN_GAP)
gap = MIN_GAP;