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authorRik van Riel <riel@redhat.com>2017-07-12 14:36:33 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-07-12 16:26:03 -0700
commitc204d21f2232d875e36b8774c36ffd027dc1d606 (patch)
tree5c2863061e09c1b22dcc956bb689ecd3a7bb0ea9 /arch/x86
parent2c8340eda45cee1784f7b29e6d7dcc740ea3d02a (diff)
downloadlinux-c204d21f2232d875e36b8774c36ffd027dc1d606.tar.bz2
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/x86')
-rw-r--r--arch/x86/mm/mmap.c7
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)