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From:   Eric Biggers <ebiggers@kernel.org>
To:     linux-crypto@vger.kernel.org
Cc:     Dan Carpenter <dan.carpenter@oracle.com>,
        Neil Horman <nhorman@tuxdriver.com>,
        Corentin Labbe <clabbe@baylibre.com>, stable@vger.kernel.org
Subject: [PATCH] crypto: rng - fix crypto_rng_reset() refcounting when !CRYPTO_STATS
Date:   Sun, 21 Mar 2021 22:07:48 -0700
Message-Id: <20210322050748.265604-1-ebiggers@kernel.org>
MIME-Version: 1.0
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From: Eric Biggers <ebiggers@google.com>

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>
---
 crypto/rng.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/crypto/rng.c b/crypto/rng.c
index a888d84b524a4..fea082b25fe4b 100644
--- a/crypto/rng.c
+++ b/crypto/rng.c
@@ -34,22 +34,18 @@ int crypto_rng_reset(struct crypto_rng *tfm, const u8 *seed, unsigned int slen)
 	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:
-- 
2.31.0