crypto: skcipher - Fix -Wstringop-truncation warnings

As of GCC 9.0.0 the build is reporting warnings like:

    crypto/ablkcipher.c: In function ‘crypto_ablkcipher_report’:
    crypto/ablkcipher.c:374:2: warning: ‘strncpy’ specified bound 64 equals destination size [-Wstringop-truncation]
      strncpy(rblkcipher.geniv, alg->cra_ablkcipher.geniv ?: "<default>",
      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
       sizeof(rblkcipher.geniv));
       ~~~~~~~~~~~~~~~~~~~~~~~~~

This means the strnycpy might create a non null terminated string.  Fix this by
explicitly performing '\0' termination.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Eric Biggers <ebiggers3@gmail.com>
Cc: Nick Desaulniers <nick.desaulniers@gmail.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/ablkcipher.c

@@ -373,6 +373,7 @@ static int crypto_ablkcipher_report(struct sk_buff *skb, struct crypto_alg *alg)
 	strncpy(rblkcipher.type, "ablkcipher", sizeof(rblkcipher.type));
 	strncpy(rblkcipher.geniv, alg->cra_ablkcipher.geniv ?: "<default>",
 		sizeof(rblkcipher.geniv));
+	rblkcipher.geniv[sizeof(rblkcipher.geniv) - 1] = '\0';
 
 	rblkcipher.blocksize = alg->cra_blocksize;
 	rblkcipher.min_keysize = alg->cra_ablkcipher.min_keysize;
@@ -447,6 +448,7 @@ static int crypto_givcipher_report(struct sk_buff *skb, struct crypto_alg *alg)
 	strncpy(rblkcipher.type, "givcipher", sizeof(rblkcipher.type));
 	strncpy(rblkcipher.geniv, alg->cra_ablkcipher.geniv ?: "<built-in>",
 		sizeof(rblkcipher.geniv));
+	rblkcipher.geniv[sizeof(rblkcipher.geniv) - 1] = '\0';
 
 	rblkcipher.blocksize = alg->cra_blocksize;
 	rblkcipher.min_keysize = alg->cra_ablkcipher.min_keysize;

crypto/blkcipher.c

@@ -512,6 +512,7 @@ static int crypto_blkcipher_report(struct sk_buff *skb, struct crypto_alg *alg)
 	strncpy(rblkcipher.type, "blkcipher", sizeof(rblkcipher.type));
 	strncpy(rblkcipher.geniv, alg->cra_blkcipher.geniv ?: "<default>",
 		sizeof(rblkcipher.geniv));
+	rblkcipher.geniv[sizeof(rblkcipher.geniv) - 1] = '\0';
 
 	rblkcipher.blocksize = alg->cra_blocksize;
 	rblkcipher.min_keysize = alg->cra_blkcipher.min_keysize;