From: Eric Biggers <ebiggers@kernel.org>
Date: Mon, 20 Apr 2026 06:34:15 +0000 (-0700)
Subject: crypto: drbg - Separate "reseed" case in drbg_kcapi_seed()
X-Git-Url: http://git.ipfire.org/gitweb/index.cgi?a=commitdiff_plain;h=ad8883374f34809f04d6839b9e7efe0afa5e92cd;p=thirdparty%2Fkernel%2Flinux.git

crypto: drbg - Separate "reseed" case in drbg_kcapi_seed()

Clearly separate the code for the "reseed" and "instantiate" cases,
since what they need to do is quite different.

Note that the mutex guard makes the mutex start being held during the
call to drbg_uninstantiate(), which is fine.

Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---

diff --git a/crypto/drbg.c b/crypto/drbg.c
index 763c14e3786c6..a9d586107ebed 100644
--- a/crypto/drbg.c
+++ b/crypto/drbg.c
@@ -577,11 +577,13 @@ static int drbg_kcapi_seed(struct crypto_rng *tfm,
 	static const u8 initial_key[DRBG_STATE_LEN]; /* all zeroes */
 	struct drbg_state *drbg = crypto_rng_ctx(tfm);
 	int ret;
-	bool reseed = true;
 
 	pr_devel("DRBG: Initializing DRBG with prediction resistance %s\n",
 		 str_enabled_disabled(pr));
-	mutex_lock(&drbg->drbg_mutex);
+	guard(mutex)(&drbg->drbg_mutex);
+
+	if (drbg->instantiated)
+		return drbg_seed(drbg, pers, pers_len, /* reseed= */ true);
 
 	/* 9.1 step 1 is implicit with the selected DRBG type */
 
@@ -592,32 +594,24 @@ static int drbg_kcapi_seed(struct crypto_rng *tfm,
 
 	/* 9.1 step 4 is implicit in DRBG_SEC_STRENGTH */
 
-	if (!drbg->instantiated) {
-		drbg->instantiated = true;
-		drbg->pr = pr;
-		drbg->seeded = DRBG_SEED_STATE_UNSEEDED;
-		drbg->last_seed_time = 0;
-		drbg->reseed_threshold = DRBG_MAX_REQUESTS;
-		memset(drbg->V, 1, DRBG_STATE_LEN);
-		hmac_sha512_preparekey(&drbg->key, initial_key, DRBG_STATE_LEN);
-
-		ret = drbg_prepare_hrng(drbg);
-		if (ret)
-			goto free_everything;
-
-		reseed = false;
-	}
-
-	ret = drbg_seed(drbg, pers, pers_len, reseed);
+	drbg->instantiated = true;
+	drbg->pr = pr;
+	drbg->seeded = DRBG_SEED_STATE_UNSEEDED;
+	drbg->last_seed_time = 0;
+	drbg->reseed_threshold = DRBG_MAX_REQUESTS;
+	memset(drbg->V, 1, DRBG_STATE_LEN);
+	hmac_sha512_preparekey(&drbg->key, initial_key, DRBG_STATE_LEN);
 
-	if (ret && !reseed)
+	ret = drbg_prepare_hrng(drbg);
+	if (ret)
+		goto free_everything;
+	ret = drbg_seed(drbg, pers, pers_len, /* reseed= */ false);
+	if (ret)
 		goto free_everything;
 
-	mutex_unlock(&drbg->drbg_mutex);
 	return ret;
 
 free_everything:
-	mutex_unlock(&drbg->drbg_mutex);
 	drbg_uninstantiate(drbg);
 	return ret;
 }