Messages in this thread Patch in this message | | | From | riel@redhat ... | Subject | [PATCH 1/3] x86/mmap: properly account for stack randomization in mmap_base | Date | Thu, 22 Jun 2017 16:00:31 -0400 |
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From: Rik van Riel <riel@redhat.com>
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.
From Daniel Micay's linux-hardened tree.
Reported-by: Florian Weimer <fweimer@redhat.com> Signed-off-by: Daniel Micay <danielmicay@gmail.com> Signed-off-by: Rik van Riel <riel@redhat.com> --- arch/x86/mm/mmap.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c index 19ad095b41df..7c35dd73dbd4 100644 --- a/arch/x86/mm/mmap.c +++ b/arch/x86/mm/mmap.c @@ -95,13 +95,18 @@ 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) -- 2.9.4
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