crypto: rng - ensure that the RNG is ready before using

Otherwise, we might be seeding the RNG using bad randomness, which is
dangerous. The one use of this function from within the kernel -- not
from userspace -- is being removed (keys/big_key), so that call site
isn't relevant in assessing this.

Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/crypto/rng.c b/crypto/rng.c
index 5e8469244960f85b52640fda18b561238ccdcce3..b4a618668161dc93b0b7643393a8e558287ba39f 100644 (file)
--- a/crypto/rng.c
+++ b/crypto/rng.c
@@ -43,12 +43,14 @@ 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;
 }