Commit cf92251d authored by Rik van Riel's avatar Rik van Riel Committed by Linus Torvalds

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.comSigned-off-by: default avatarDaniel Micay <danielmicay@gmail.com>
Signed-off-by: default avatarRik van Riel <riel@redhat.com>
Reported-by: default avatarFlorian 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c204d21f
...@@ -35,7 +35,7 @@ ...@@ -35,7 +35,7 @@
* Leave enough space between the mmap area and the stack to honour ulimit in * Leave enough space between the mmap area and the stack to honour ulimit in
* the face of randomisation. * 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) #define MAX_GAP (STACK_TOP/6*5)
static int mmap_is_legacy(void) static int mmap_is_legacy(void)
...@@ -65,6 +65,11 @@ unsigned long arch_mmap_rnd(void) ...@@ -65,6 +65,11 @@ unsigned long arch_mmap_rnd(void)
static unsigned long mmap_base(unsigned long rnd) static unsigned long mmap_base(unsigned long rnd)
{ {
unsigned long gap = rlimit(RLIMIT_STACK); 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) if (gap < MIN_GAP)
gap = MIN_GAP; gap = MIN_GAP;
......
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