linux-kernel - [PATCH] crypto: fix null-ptr-dereference in rng

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Message-Id: <20250930032824.690214-1-sunyiqixm@gmail.com>
Date: Tue, 30 Sep 2025 11:28:24 +0800
From: Dave Sun <sunyiqixm@...il.com>
To: herbert@...dor.apana.org.au,
	davem@...emloft.net
Cc: linux-crypto@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Dave Sun <sunyiqixm@...il.com>
Subject: [PATCH] crypto: fix null-ptr-dereference in rng_setentropy

When CONFIG_CRYPTO_USER_API_RNG_CAVP is enable,
algif_type_rng->setentropy = rng_setentropy.
If we setsockopt on a af_alg socket binding a rng
algorithm with ALG_SET_DRBG_ENTROPY opt, kernel will
run to ->set_ent in rng_setentropy.

Since struct rng_alg like jent_alg dose not set set_ent
which default value is 0, null-ptr-dereference will happen.

Check ->set_ent before call it.

Signed-off-by: Yiqi Sun <sunyiqixm@...il.com>
---
 crypto/algif_rng.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/crypto/algif_rng.c b/crypto/algif_rng.c
index 10c41adac3b1..26a75c54192b 100644
--- a/crypto/algif_rng.c
+++ b/crypto/algif_rng.c
@@ -303,6 +303,9 @@ static int __maybe_unused rng_setentropy(void *private, sockptr_t entropy,
 			return PTR_ERR(kentropy);
 	}
 
+	if (!crypto_rng_alg(pctx->drng)->set_ent)
+		return -EOPNOTSUPP;
+
 	crypto_rng_alg(pctx->drng)->set_ent(pctx->drng, kentropy, len);
 	/*
 	 * Since rng doesn't perform any memory management for the entropy
-- 
2.34.1