crypto: skcipher - Fix -Wstringop-truncation warnings

[ Upstream commit cefd769fd0192c84d638f66da202459ed8ad63ba ]

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>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/crypto/blkcipher.c b/crypto/blkcipher.c
index 27f9866..59a0936 100644
--- a/crypto/blkcipher.c
+++ b/crypto/blkcipher.c
@@ -510,6 +510,7 @@
 	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;