From: Jason A. Donenfeld <Jason@zx2c4.com>
Date: Mon, 26 Sep 2022 16:32:25 +0000 (+0200)
Subject: kfence: use better stack hash seed
X-Git-Tag: v6.1-rc1~91^2~7
X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=08475dab7cf5b610ea2420828e97c54f5f370d7d;p=linux-block.git

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 c252081b11df..239b1b4b094f 100644
--- 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)