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authorAndrey Konovalov <andreyknvl@google.com>2019-02-20 22:20:15 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2019-02-21 09:01:00 -0800
commit3f41b609382388f95c0a05b69b8db0d706adafb4 (patch)
treecf5fed9746400cbda15f47acd7acceab80aa1fd5 /mm
parent1062af920c07f5b54cf5060fde3339da6df0cf6b (diff)
kasan: fix random seed generation for tag-based mode
There are two issues with assigning random percpu seeds right now: 1. We use for_each_possible_cpu() to iterate over cpus, but cpumask is not set up yet at the moment of kasan_init(), and thus we only set the seed for cpu #0. 2. A call to get_random_u32() always returns the same number and produces a message in dmesg, since the random subsystem is not yet initialized. Fix 1 by calling kasan_init_tags() after cpumask is set up. Fix 2 by using get_cycles() instead of get_random_u32(). This gives us lower quality random numbers, but it's good enough, as KASAN is meant to be used as a debugging tool and not a mitigation. Link: http://lkml.kernel.org/r/1f815cc914b61f3516ed4cc9bfd9eeca9bd5d9de.1550677973.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/kasan/tags.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/kasan/tags.c b/mm/kasan/tags.c
index 0777649e07c4..63fca3172659 100644
--- a/mm/kasan/tags.c
+++ b/mm/kasan/tags.c
@@ -46,7 +46,7 @@ void kasan_init_tags(void)
int cpu;
for_each_possible_cpu(cpu)
- per_cpu(prng_state, cpu) = get_random_u32();
+ per_cpu(prng_state, cpu) = (u32)get_cycles();
}
/*