gfs2: Switch from strlcpy to strscpy

Switch from strlcpy to strscpy and make sure that @count is the size of
the smaller of the source and destination buffers.  This prevents
reading beyond the end of the source buffer when the source string isn't
null terminated.

Found by a modified version of syzkaller.

Suggested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

Author: Andreas Gruenbacher

fs/gfs2/ops_fstype.c

@@ -381,8 +381,10 @@ static int init_names(struct gfs2_sbd *sdp, int silent)
 	if (!table[0])
 		table = sdp->sd_vfs->s_id;
 
-	strlcpy(sdp->sd_proto_name, proto, GFS2_FSNAME_LEN);
-	strlcpy(sdp->sd_table_name, table, GFS2_FSNAME_LEN);
+	BUILD_BUG_ON(GFS2_LOCKNAME_LEN > GFS2_FSNAME_LEN);
+
+	strscpy(sdp->sd_proto_name, proto, GFS2_LOCKNAME_LEN);
+	strscpy(sdp->sd_table_name, table, GFS2_LOCKNAME_LEN);
 
 	table = sdp->sd_table_name;
 	while ((table = strchr(table, '/')))
@@ -1439,13 +1441,13 @@ static int gfs2_parse_param(struct fs_context *fc, struct fs_parameter *param)
 
 	switch (o) {
 	case Opt_lockproto:
-		strlcpy(args->ar_lockproto, param->string, GFS2_LOCKNAME_LEN);
+		strscpy(args->ar_lockproto, param->string, GFS2_LOCKNAME_LEN);
 		break;
 	case Opt_locktable:
-		strlcpy(args->ar_locktable, param->string, GFS2_LOCKNAME_LEN);
+		strscpy(args->ar_locktable, param->string, GFS2_LOCKNAME_LEN);
 		break;
 	case Opt_hostdata:
-		strlcpy(args->ar_hostdata, param->string, GFS2_LOCKNAME_LEN);
+		strscpy(args->ar_hostdata, param->string, GFS2_LOCKNAME_LEN);
 		break;
 	case Opt_spectator:
 		args->ar_spectator = 1;