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crypto: jitterentropy - replace long-held spinlock with mutex

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[ Upstream commit 01d798e9fe ]

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: bb5530e408 ("crypto: jitterentropy - add jitterentropy RNG")
Reported-by: Yifan Wu <yifanwucs@gmail.com>
Reported-by: Juefei Pu <tomapufckgml@gmail.com>
Reported-by: Yuan Tan <yuantan098@gmail.com>
Suggested-by: Xin Liu <bird@lzu.edu.cn>
Signed-off-by: Haixin Xu <jerryxucs@gmail.com>
Reviewed-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Haixin Xu
2026-05-23 13:06:43 +02:00
committed by Greg Kroah-Hartman
parent 3ab9ab2dc1
commit ff734dbd9e
1 changed files with 7 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files
crypto/jitterentropy-kcapi.c
+7 -7
View File
@@ -42,6 +42,7 @@
#include <linux/fips.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/time.h>
#include <crypto/internal/rng.h>
@@ -193,7 +194,7 @@ int jent_read_random_block(void *hash_state, char *dst, unsigned int dst_len)
***************************************************************************/
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 = crypto_tfm_ctx(tfm);
spin_lock(&rng->jent_lock);
mutex_lock(&rng->jent_lock);
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 = NULL;
spin_unlock(&rng->jent_lock);
mutex_unlock(&rng->jent_lock);
}
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 = 0;
spin_lock_init(&rng->jent_lock);
mutex_init(&rng->jent_lock);
/*
* Use SHA3-256 as conditioner. We allocate only the generic
@@ -265,7 +266,6 @@ static int jent_kcapi_init(struct crypto_tfm *tfm)
goto err;
}
spin_lock_init(&rng->jent_lock);
return 0;
err:
@@ -280,7 +280,7 @@ static int jent_kcapi_random(struct crypto_rng *tfm,
struct jitterentropy *rng = crypto_rng_ctx(tfm);
int ret = 0;
spin_lock(&rng->jent_lock);
mutex_lock(&rng->jent_lock);
ret = jent_read_entropy(rng->entropy_collector, rdata, dlen);
@@ -306,7 +306,7 @@ static int jent_kcapi_random(struct crypto_rng *tfm,
ret = -EINVAL;
}
spin_unlock(&rng->jent_lock);
mutex_unlock(&rng->jent_lock);
return ret;
}