On Fri, Sep 10, 2021 at 01:41:01PM +0200, mwilck@xxxxxxxx wrote:
> From: Martin Wilck <mwilck@xxxxxxxx>
>
> 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 <bmarzins@xxxxxxxxxx>
> Signed-off-by: Martin Wilck <mwilck@xxxxxxxx>
> ---
> multipathd/uxlsnr.c | 12 +++++++++---
> 1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/multipathd/uxlsnr.c b/multipathd/uxlsnr.c
> index 20efbd3..7e88538 100644
> --- a/multipathd/uxlsnr.c
> +++ b/multipathd/uxlsnr.c
> @@ -393,7 +393,7 @@ 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;
> @@ -410,6 +410,12 @@ 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)
> @@ -423,7 +429,7 @@ 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);
> @@ -434,7 +440,7 @@ 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;
> --
> 2.33.0
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