NFSD: Fix strncpy() fortify warning

In function ‘strncpy’,
    inlined from ‘nfsd4_ssc_setup_dul’ at /home/cel/src/linux/manet/fs/nfsd/nfs4proc.c:1392:3,
    inlined from ‘nfsd4_interssc_connect’ at /home/cel/src/linux/manet/fs/nfsd/nfs4proc.c:1489:11:
/home/cel/src/linux/manet/include/linux/fortify-string.h:52:33: warning: ‘__builtin_strncpy’ specified bound 63 equals destination size [-Wstringop-truncation]
   52 | #define __underlying_strncpy    __builtin_strncpy
      |                                 ^
/home/cel/src/linux/manet/include/linux/fortify-string.h:89:16: note: in expansion of macro ‘__underlying_strncpy’
   89 |         return __underlying_strncpy(p, q, size);
      |                ^~~~~~~~~~~~~~~~~~~~
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfs4proc.c

@@ -1389,7 +1389,7 @@ static __be32 nfsd4_ssc_setup_dul(struct nfsd_net *nn, char *ipaddr,
 		return 0;
 	}
 	if (work) {
-		strncpy(work->nsui_ipaddr, ipaddr, sizeof(work->nsui_ipaddr));
+		strlcpy(work->nsui_ipaddr, ipaddr, sizeof(work->nsui_ipaddr) - 1);
 		refcount_set(&work->nsui_refcnt, 2);
 		work->nsui_busy = true;
 		list_add_tail(&work->nsui_list, &nn->nfsd_ssc_mount_list);

include/linux/nfs_ssc.h

@@ -64,7 +64,7 @@ struct nfsd4_ssc_umount_item {
 	refcount_t nsui_refcnt;
 	unsigned long nsui_expire;
 	struct vfsmount *nsui_vfsmount;
-	char nsui_ipaddr[RPC_MAX_ADDRBUFLEN];
+	char nsui_ipaddr[RPC_MAX_ADDRBUFLEN + 1];
 };
 #endif