crypto: user - re-add size check for CRYPTO_MSG_GETALG

Commit 9aa867e465 ("crypto: user - Add CRYPTO_MSG_DELRNG")
accidentally removed the minimum size check for CRYPTO_MSG_GETALG
netlink messages. This allows userland to send a truncated
CRYPTO_MSG_GETALG message as short as a netlink header only making
crypto_report() operate on uninitialized memory by accessing data
beyond the end of the netlink message.

Fix this be re-adding the minimum required size of CRYPTO_MSG_GETALG
messages to the crypto_msg_min[] array.

Fixes: 9aa867e465 ("crypto: user - Add CRYPTO_MSG_DELRNG")
Cc: stable@vger.kernel.org	# v4.2
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/crypto_user.c

@@ -455,6 +455,7 @@ static const int crypto_msg_min[CRYPTO_NR_MSGTYPES] = {
 	[CRYPTO_MSG_NEWALG	- CRYPTO_MSG_BASE] = MSGSIZE(crypto_user_alg),
 	[CRYPTO_MSG_DELALG	- CRYPTO_MSG_BASE] = MSGSIZE(crypto_user_alg),
 	[CRYPTO_MSG_UPDATEALG	- CRYPTO_MSG_BASE] = MSGSIZE(crypto_user_alg),
+	[CRYPTO_MSG_GETALG	- CRYPTO_MSG_BASE] = MSGSIZE(crypto_user_alg),
 	[CRYPTO_MSG_DELRNG	- CRYPTO_MSG_BASE] = 0,
 };