knfsd: rpc: fix server-side wrapping of krb5i replies

It's not necessarily correct to assume that the xdr_buf used to hold the
server's reply must have page data whenever it has tail data.

And there's no need for us to deal with that case separately anyway.
Acked-by: "J. Bruce Fields" <bfields@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@suse.de>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

net/sunrpc/auth_gss/svcauth_gss.c

@@ -1196,13 +1196,7 @@ svcauth_gss_wrap_resp_integ(struct svc_rqst *rqstp)
 	if (xdr_buf_subsegment(resbuf, &integ_buf, integ_offset,
 				integ_len))
 		BUG();
-	if (resbuf->page_len == 0
-			&& resbuf->head[0].iov_len + RPC_MAX_AUTH_SIZE
-			< PAGE_SIZE) {
-		BUG_ON(resbuf->tail[0].iov_len);
-		/* Use head for everything */
-		resv = &resbuf->head[0];
-	} else if (resbuf->tail[0].iov_base == NULL) {
+	if (resbuf->tail[0].iov_base == NULL) {
 		if (resbuf->head[0].iov_len + RPC_MAX_AUTH_SIZE > PAGE_SIZE)
 			goto out_err;
 		resbuf->tail[0].iov_base = resbuf->head[0].iov_base