Merge branch 'js/packet-read-line-check-null'

Some low level protocol codepath could crash when they get an
unexpected flush packet, which is now fixed.

* js/packet-read-line-check-null:
  always check for NULL return from packet_read_line()
  correct error messages for NULL packet_read_line()

builtin/archive.c

@@ -55,7 +55,7 @@ static int run_remote_archiver(int argc, const char **argv,
 
 	buf = packet_read_line(fd[0], NULL);
 	if (!buf)
-		die(_("git archive: expected ACK/NAK, got EOF"));
+		die(_("git archive: expected ACK/NAK, got a flush packet"));
 	if (strcmp(buf, "ACK")) {
 		if (starts_with(buf, "NACK "))
 			die(_("git archive: NACK %s"), buf + 5);

fetch-pack.c

@@ -261,8 +261,8 @@ static enum ack_type get_ack(int fd, struct object_id *result_oid)
 	char *line = packet_read_line(fd, &len);
 	const char *arg;
 
-	if (!len)
-		die(_("git fetch-pack: expected ACK/NAK, got EOF"));
+	if (!line)
+		die(_("git fetch-pack: expected ACK/NAK, got a flush packet"));
 	if (!strcmp(line, "NAK"))
 		return NAK;
 	if (skip_prefix(line, "ACK ", &arg)) {

remote-curl.c

@@ -351,6 +351,8 @@ static struct discovery *discover_refs(const char *service, int for_push)
 		 * pkt-line matches our request.
 		 */
 		line = packet_read_line_buf(&last->buf, &last->len, NULL);
+		if (!line)
+			die("invalid server response; expected service, got flush packet");
 
 		strbuf_reset(&exp);
 		strbuf_addf(&exp, "# service=%s", service);

send-pack.c

@@ -137,6 +137,8 @@ static int pack_objects(int fd, struct ref *refs, struct oid_array *extra, struc
 static int receive_unpack_status(int in)
 {
 	const char *line = packet_read_line(in, NULL);
+	if (!line)
+		return error(_("unexpected flush packet while reading remote unpack status"));
 	if (!skip_prefix(line, "unpack ", &line))
 		return error(_("unable to parse remote unpack status: %s"), line);
 	if (strcmp(line, "ok"))