kfence: use better stack hash seed

As of the prior commit, the RNG will have incorporated both a cycle
counter value and RDRAND, in addition to various other environmental
noise. Therefore, using get_random_u32() will supply a stronger seed
than simply using random_get_entropy(). N.B.: random_get_entropy()
should be considered an internal API of random.c and not generally
consumed.

Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Marco Elver <elver@google.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index c252081b11dfe57f5d608f385785787c06b72347..239b1b4b094fa8e5edfed9519325cd805cae73a8 100644 (file)
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -864,7 +864,7 @@ static void kfence_init_enable(void)
 
 void __init kfence_init(void)
 {
-       stack_hash_seed = (u32)random_get_entropy();
+       stack_hash_seed = get_random_u32();
 
        /* Setting kfence_sample_interval to 0 on boot disables KFENCE. */
        if (!kfence_sample_interval)