SUNRPC: Don't use variable length automatic arrays in kernel code

Replace the variable length array in the RPCSEC_GSS crypto code with
a fixed length one. The size should be bounded by the variable
GSS_KRB5_MAX_BLOCKSIZE, so use that.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/net/sunrpc/auth_gss/gss_krb5_crypto.c b/net/sunrpc/auth_gss/gss_krb5_crypto.c
index 9576f35..0f43e89 100644
--- a/net/sunrpc/auth_gss/gss_krb5_crypto.c
+++ b/net/sunrpc/auth_gss/gss_krb5_crypto.c
@@ -600,11 +600,14 @@
 	u32 ret;
 	struct scatterlist sg[1];
 	struct blkcipher_desc desc = { .tfm = cipher, .info = iv };
-	u8 data[crypto_blkcipher_blocksize(cipher) * 2];
+	u8 data[GSS_KRB5_MAX_BLOCKSIZE * 2];
 	struct page **save_pages;
 	u32 len = buf->len - offset;
 
-	BUG_ON(len > crypto_blkcipher_blocksize(cipher) * 2);
+	if (len > ARRAY_SIZE(data)) {
+		WARN_ON(0);
+		return -ENOMEM;
+	}
 
 	/*
 	 * For encryption, we want to read from the cleartext