[PATCH 03/14] crypto: jitterentropy - Move health check to first use

[Eric Biggers <ebiggers@kernel.org>]

Building jitterentropy into the kernel causes the expensive health check
to run on boot, even if jitterentropy is never used.

With the upcoming addition of direct linking, this problem would get
worse since it will happen even if jitterentropy is built as a module.

To fix this, do the health check on first use instead of in module_init.

Note that this shouldn't have any impact on FIPS 140-3 certifiability.
A failed health check now panics on first use instead of on boot, but
that is acceptable.

Signed-off-by: Eric Biggers <ebiggers@kernel.org>
---
 crypto/jitterentropy-kcapi.c | 72 ++++++++++++++++++++++++++----------
 1 file changed, 53 insertions(+), 19 deletions(-)

diff --git a/crypto/jitterentropy-kcapi.c b/crypto/jitterentropy-kcapi.c
index 652852649a312..84c2c74240a0a 100644
--- a/crypto/jitterentropy-kcapi.c
+++ b/crypto/jitterentropy-kcapi.c
@@ -178,6 +178,54 @@ struct jitterentropy {
 	struct sha3_ctx hash_state;
 };
 
+static int jent_init_err;
+
+static void jent_init_once(void)
+{
+	struct sha3_ctx hash_state;
+	int err;
+
+	sha3_256_init(&hash_state);
+	err = jent_entropy_init(CONFIG_CRYPTO_JITTERENTROPY_OSR, 0, &hash_state,
+				NULL);
+	memzero_explicit(&hash_state, sizeof(hash_state));
+	if (err) {
+		/* Handle permanent health test error */
+		if (fips_enabled)
+			panic("jitterentropy: Initialization failed with host not compliant with requirements: %d\n",
+			      err);
+
+		pr_info("jitterentropy: Initialization failed with host not compliant with requirements: %d\n",
+			err);
+		jent_init_err = err;
+	}
+}
+
+static int jent_init(void)
+{
+	static DEFINE_MUTEX(jent_init_mutex);
+	static bool initialized;
+
+	/*
+	 * To avoid lockdep reports of inconsistent ordering of drbg_mutex and
+	 * once_mutex, implement one-time-init locally instead of using
+	 * DO_ONCE_SLEEPABLE.
+	 */
+	guard(mutex)(&jent_init_mutex);
+	if (!initialized) {
+		jent_init_once();
+		initialized = true;
+	}
+	if (jent_init_err) {
+		/*
+		 * jent_init_err is a private custom error code from
+		 * jitterentropy.c.  Select an errno value instead.
+		 */
+		return -EOPNOTSUPP;
+	}
+	return 0;
+}
+
 static void jent_kcapi_cleanup(struct crypto_tfm *tfm)
 {
 	struct jitterentropy *rng = crypto_tfm_ctx(tfm);
@@ -195,7 +243,11 @@ static void jent_kcapi_cleanup(struct crypto_tfm *tfm)
 static int jent_kcapi_init(struct crypto_tfm *tfm)
 {
 	struct jitterentropy *rng = crypto_tfm_ctx(tfm);
-	int ret = 0;
+	int ret;
+
+	ret = jent_init();
+	if (ret)
+		return ret;
 
 	mutex_init(&rng->jent_lock);
 
@@ -277,25 +329,7 @@ static struct rng_alg jent_alg = {
 
 static int __init jent_mod_init(void)
 {
-	struct sha3_ctx hash_state;
-	int ret = 0;
-
 	jent_testing_init();
-
-	sha3_256_init(&hash_state);
-
-	ret = jent_entropy_init(CONFIG_CRYPTO_JITTERENTROPY_OSR, 0, &hash_state,
-				NULL);
-	memzero_explicit(&hash_state, sizeof(hash_state));
-	if (ret) {
-		/* Handle permanent health test error */
-		if (fips_enabled)
-			panic("jitterentropy: Initialization failed with host not compliant with requirements: %d\n", ret);
-
-		jent_testing_exit();
-		pr_info("jitterentropy: Initialization failed with host not compliant with requirements: %d\n", ret);
-		return -EFAULT;
-	}
 	return crypto_register_rng(&jent_alg);
 }
 
-- 
2.56.0