diff options
| author | Andrey Konovalov <andreyknvl@google.com> | 2019-02-20 22:20:15 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-02-21 09:01:00 -0800 |
| commit | 3f41b609382388f95c0a05b69b8db0d706adafb4 (patch) | |
| tree | cf5fed9746400cbda15f47acd7acceab80aa1fd5 | |
| parent | 1062af920c07f5b54cf5060fde3339da6df0cf6b (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>
| -rw-r--r-- | arch/arm64/kernel/setup.c | 3 | ||||
| -rw-r--r-- | arch/arm64/mm/kasan_init.c | 2 | ||||
| -rw-r--r-- | mm/kasan/tags.c | 2 |
3 files changed, 4 insertions, 3 deletions
diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c index d09ec76f08cf..009849328289 100644 --- a/arch/arm64/kernel/setup.c +++ b/arch/arm64/kernel/setup.c @@ -339,6 +339,9 @@ void __init setup_arch(char **cmdline_p) smp_init_cpus(); smp_build_mpidr_hash(); + /* Init percpu seeds for random tags after cpus are set up. */ + kasan_init_tags(); + #ifdef CONFIG_ARM64_SW_TTBR0_PAN /* * Make sure init_thread_info.ttbr0 always generates translation diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c index 4b55b15707a3..f37a86d2a69d 100644 --- a/arch/arm64/mm/kasan_init.c +++ b/arch/arm64/mm/kasan_init.c @@ -252,8 +252,6 @@ void __init kasan_init(void) memset(kasan_early_shadow_page, KASAN_SHADOW_INIT, PAGE_SIZE); cpu_replace_ttbr1(lm_alias(swapper_pg_dir)); - kasan_init_tags(); - /* At this point kasan is fully initialized. Enable error messages */ init_task.kasan_depth = 0; pr_info("KernelAddressSanitizer initialized\n"); 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(); } /* |