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Mon, 30 Mar 2026 00:24:12 -0700 (PDT) Received: from cachyos-x8664.sustech.edu.cn ([116.6.234.169]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b2427c3a4esm87002045ad.78.2026.03.30.00.24.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 30 Mar 2026 00:24:12 -0700 (PDT) From: Haixin Xu To: linux-crypto@vger.kernel.org Cc: linux-kernel@vger.kernel.org, herbert@gondor.apana.org.au, davem@davemloft.net, smueller@chronox.de, yifanwucs@gmail.com, tomapufckgml@gmail.com, yuantan098@gmail.com, bird@lzu.edu.cn, jerryxucs@gmail.com Subject: [PATCH 1/1] crypto: jitterentropy - replace long-held spinlock with mutex Date: Mon, 30 Mar 2026 15:23:46 +0800 Message-ID: <9a8ef1cbcc68b752a495acf0a23e7095eb0a7796.1774854094.git.jerryxucs@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" jent_kcapi_random() serializes the shared jitterentropy state, but it currently holds a spinlock across the jent_read_entropy() call. That path performs expensive jitter collection and SHA3 conditioning, so parallel readers can trigger stalls as contending waiters spin for the same lock. To prevent non-preemptible lock hold, replace rng->jent_lock with a mutex so contended readers sleep instead of spinning on a shared lock held across expensive entropy generation. Fixes: bb5530e40824 ("crypto: jitterentropy - add jitterentropy RNG") Reported-by: Yifan Wu Reported-by: Juefei Pu Reported-by: Yuan Tan Suggested-by: Xin Liu Signed-off-by: Haixin Xu --- crypto/jitterentropy-kcapi.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/crypto/jitterentropy-kcapi.c b/crypto/jitterentropy-kcapi.c index 7c880cf34c52..5edc6d285aa1 100644 --- a/crypto/jitterentropy-kcapi.c +++ b/crypto/jitterentropy-kcapi.c @@ -42,6 +42,7 @@ #include #include #include +#include #include #include #include @@ -193,7 +194,7 @@ int jent_read_random_block(void *hash_state, char *dst,= unsigned int dst_len) *************************************************************************= **/ =20 struct jitterentropy { - spinlock_t jent_lock; + struct mutex jent_lock; struct rand_data *entropy_collector; struct crypto_shash *tfm; struct shash_desc *sdesc; @@ -203,7 +204,7 @@ static void jent_kcapi_cleanup(struct crypto_tfm *tfm) { struct jitterentropy *rng =3D crypto_tfm_ctx(tfm); =20 - spin_lock(&rng->jent_lock); + mutex_lock(&rng->jent_lock); =20 if (rng->sdesc) { shash_desc_zero(rng->sdesc); @@ -218,7 +219,7 @@ static void jent_kcapi_cleanup(struct crypto_tfm *tfm) if (rng->entropy_collector) jent_entropy_collector_free(rng->entropy_collector); rng->entropy_collector =3D NULL; - spin_unlock(&rng->jent_lock); + mutex_unlock(&rng->jent_lock); } =20 static int jent_kcapi_init(struct crypto_tfm *tfm) @@ -228,7 +229,7 @@ static int jent_kcapi_init(struct crypto_tfm *tfm) struct shash_desc *sdesc; int size, ret =3D 0; =20 - spin_lock_init(&rng->jent_lock); + mutex_init(&rng->jent_lock); =20 /* Use SHA3-256 as conditioner */ hash =3D crypto_alloc_shash(JENT_CONDITIONING_HASH, 0, 0); @@ -257,7 +258,6 @@ static int jent_kcapi_init(struct crypto_tfm *tfm) goto err; } =20 - spin_lock_init(&rng->jent_lock); return 0; =20 err: @@ -272,7 +272,7 @@ static int jent_kcapi_random(struct crypto_rng *tfm, struct jitterentropy *rng =3D crypto_rng_ctx(tfm); int ret =3D 0; =20 - spin_lock(&rng->jent_lock); + mutex_lock(&rng->jent_lock); =20 ret =3D jent_read_entropy(rng->entropy_collector, rdata, dlen); =20 @@ -298,7 +298,7 @@ static int jent_kcapi_random(struct crypto_rng *tfm, ret =3D -EINVAL; } =20 - spin_unlock(&rng->jent_lock); + mutex_unlock(&rng->jent_lock); =20 return ret; } --=20 2.53.0