diff options
| author | Rik van Riel <riel@redhat.com> | 2017-07-12 14:36:33 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-07-12 16:26:03 -0700 |
| commit | c204d21f2232d875e36b8774c36ffd027dc1d606 (patch) | |
| tree | 5c2863061e09c1b22dcc956bb689ecd3a7bb0ea9 /arch | |
| parent | 2c8340eda45cee1784f7b29e6d7dcc740ea3d02a (diff) | |
x86/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/20170622200033.25714-2-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>
Acked-by: 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')
| -rw-r--r-- | arch/x86/mm/mmap.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c index 797295e792b2..229d04a83f85 100644 --- a/arch/x86/mm/mmap.c +++ b/arch/x86/mm/mmap.c @@ -92,13 +92,18 @@ unsigned long arch_mmap_rnd(void) static unsigned long mmap_base(unsigned long rnd, unsigned long task_size) { unsigned long gap = rlimit(RLIMIT_STACK); + unsigned long pad = stack_maxrandom_size(task_size) + stack_guard_gap; unsigned long gap_min, gap_max; + /* Values close to RLIM_INFINITY can overflow. */ + if (gap + pad > gap) + gap += pad; + /* * Top of mmap area (just below the process stack). * Leave an at least ~128 MB hole with possible stack randomization. */ - gap_min = SIZE_128M + stack_maxrandom_size(task_size); + gap_min = SIZE_128M; gap_max = (task_size / 6) * 5; if (gap < gap_min) |