[v3,15/35] multipathd: uxlsnr: handle client HUP

Commit Message

Martin Wilck Nov. 27, 2021, 3:19 p.m. UTC

From: Martin Wilck <[e-mail]>

The unix socket listener thread doesn't even look at the revents
returned by poll() while the daemon is configuring. This may cause a
closed client socket to be kept open for a long time by the server,
while the listener basically performs a busy loop, as ppoll() always
returns immediately as long as the POLLHUP condition exists.

Worse, it can happen that multipathd reads data from such a closed
client socket after the client has disconnected. See the description
of POLLHUP in poll(2).

Close connections immediately if HUP is received.

Also, use the fd in log messages to identify the client rather
than the random index.

Reviewed-by: Benjamin Marzinski <[e-mail]>
Signed-off-by: Martin Wilck <[e-mail]>
---
 multipathd/uxlsnr.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

Patch

diff --git a/multipathd/uxlsnr.c b/multipathd/uxlsnr.c
index 400375c..9a6ab72 100644
--- a/multipathd/uxlsnr.c
+++ b/multipathd/uxlsnr.c
@@ -392,7 +392,7 @@  void * uxsock_listen(uxsock_trigger_fn uxsock_trigger, long ux_sock,
 
 		/* see if a client wants to speak to us */
 		for (i = POLLFDS_BASE; i < n_pfds; i++) {
-			if (polls[i].revents & POLLIN) {
+			if (polls[i].revents & (POLLIN|POLLHUP|POLLERR)) {
 				struct timespec start_time;
 
 				c = NULL;
@@ -409,6 +409,12 @@  void * uxsock_listen(uxsock_trigger_fn uxsock_trigger, long ux_sock,
 						i, polls[i].fd);
 					continue;
 				}
+				if (polls[i].revents & (POLLHUP|POLLERR)) {
+					condlog(4, "cli[%d]: Disconnected",
+						c->fd);
+					dead_client(c);
+					continue;
+				}
 				get_monotonic_time(&start_time);
 				if (recv_packet_from_client(c->fd, &inbuf,
 							    uxsock_timeout)
@@ -422,7 +428,7 @@  void * uxsock_listen(uxsock_trigger_fn uxsock_trigger, long ux_sock,
 					continue;
 				}
 				condlog(4, "cli[%d]: Got request [%s]",
-					i, inbuf);
+					polls[i].fd, inbuf);
 				uxsock_trigger(inbuf, &reply, &rlen,
 					       _socket_client_is_root(c->fd),
 					       trigger_data);
@@ -433,7 +439,7 @@  void * uxsock_listen(uxsock_trigger_fn uxsock_trigger, long ux_sock,
 					} else {
 						condlog(4, "cli[%d]: "
 							"Reply [%d bytes]",
-							i, rlen);
+							polls[i].fd, rlen);
 					}
 					free(reply);
 					reply = NULL;