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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Eric Biggers <ebiggers@google.com>,
        Herbert Xu <herbert@gondor.apana.org.au>
Subject: [PATCH 5.10 248/299] crypto: rng - fix crypto_rng_reset() refcounting when !CRYPTO_STATS
Date:   Mon, 10 May 2021 12:20:45 +0200
Message-Id: <20210510102013.149821787@linuxfoundation.org>
In-Reply-To: <20210510102004.821838356@linuxfoundation.org>
References: <20210510102004.821838356@linuxfoundation.org>
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From: Eric Biggers <ebiggers@google.com>

commit 30d0f6a956fc74bb2e948398daf3278c6b08c7e9 upstream.

crypto_stats_get() is a no-op when the kernel is compiled without
CONFIG_CRYPTO_STATS, so pairing it with crypto_alg_put() unconditionally
(as crypto_rng_reset() does) is wrong.

Fix this by moving the call to crypto_stats_get() to just before the
actual algorithm operation which might need it.  This makes it always
paired with crypto_stats_rng_seed().

Fixes: eed74b3eba9e ("crypto: rng - Fix a refcounting bug in crypto_rng_reset()")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 crypto/rng.c |   10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

--- a/crypto/rng.c
+++ b/crypto/rng.c
@@ -34,22 +34,18 @@ int crypto_rng_reset(struct crypto_rng *
 	u8 *buf = NULL;
 	int err;
 
-	crypto_stats_get(alg);
 	if (!seed && slen) {
 		buf = kmalloc(slen, GFP_KERNEL);
-		if (!buf) {
-			crypto_alg_put(alg);
+		if (!buf)
 			return -ENOMEM;
-		}
 
 		err = get_random_bytes_wait(buf, slen);
-		if (err) {
-			crypto_alg_put(alg);
+		if (err)
 			goto out;
-		}
 		seed = buf;
 	}
 
+	crypto_stats_get(alg);
 	err = crypto_rng_alg(tfm)->seed(tfm, seed, slen);
 	crypto_stats_rng_seed(alg, err);
 out: