linux-kernel - [PATCH v2 2/2] kfence: use better stack hash seed

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Message-Id: <20220926213130.1508261-2-Jason@zx2c4.com>
Date:   Mon, 26 Sep 2022 23:31:30 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        kasan-dev@...glegroups.com
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Marco Elver <elver@...gle.com>
Subject: [PATCH v2 2/2] 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@...gle.com>
Cc: Dmitry Vyukov <dvyukov@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Reviewed-by: Marco Elver <elver@...gle.com>
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
---
 mm/kfence/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

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)
-- 
2.37.3