linux-kernel - [PATCH RFC v2 4/8] crypto/rng: ensure that the RNG is ready before using

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Date:   Mon,  5 Jun 2017 05:47:53 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Theodore Ts'o <tytso@....edu>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        kernel-hardening@...ts.openwall.com,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>,
        Herbert Xu <herbert@...dor.apana.org.au>
Subject: [PATCH RFC v2 4/8] crypto/rng: ensure that the RNG is ready before using

Otherwise, we might be seeding the RNG using bad randomness, which is
dangerous.

Cc: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
---
 crypto/rng.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/crypto/rng.c b/crypto/rng.c
index f46dac5288b9..e042437e64b4 100644
--- a/crypto/rng.c
+++ b/crypto/rng.c
@@ -48,12 +48,14 @@ int crypto_rng_reset(struct crypto_rng *tfm, const u8 *seed, unsigned int slen)
 		if (!buf)
 			return -ENOMEM;
 
-		get_random_bytes(buf, slen);
+		err = get_random_bytes_wait(buf, slen);
+		if (err)
+			goto out;
 		seed = buf;
 	}
 
 	err = crypto_rng_alg(tfm)->seed(tfm, seed, slen);
-
+out:
 	kzfree(buf);
 	return err;
 }
-- 
2.13.0