crypto: ecc - Fix NULL pointer deref. on no default_rng

[ Upstream commit 4c0e22c ]

If crypto_get_default_rng returns an error, the
function ecc_gen_privkey should return an error.
Instead, it currently tries to use the default_rng
nevertheless, thus creating a kernel panic with a
NULL pointer dereference.
Returning the error directly, as was supposedly
intended when looking at the code, fixes this.

Signed-off-by: Pierre Ducroquet <pinaraf@pinaraf.info>
Reviewed-by: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

crypto/ecc.c

@@ -964,7 +964,7 @@ int ecc_gen_privkey(unsigned int curve_id, unsigned int ndigits, u64 *privkey)
 	 * DRBG with a security strength of 256.
 	 */
 	if (crypto_get_default_rng())
-		err = -EFAULT;
+		return -EFAULT;
 
 	err = crypto_rng_get_bytes(crypto_default_rng, (u8 *)priv, nbytes);
 	crypto_put_default_rng();