Re: [PATCH v2] util, passt: Close daemon-lifetime fds on exit to avoid Coverity warning

[David Gibson <david@gibson.dropbear.id.au>]

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On Sun, Jun 07, 2026 at 06:19:42PM -0400, Jon Maloy wrote:
> conf_open_files() opens three file descriptors (fd_tap_listen,
> fd_repair_listen, fd_control_listen) that are held for the entire
> daemon lifetime.  Because no close() call exists for them
> anywhere, Coverity flags each as INCOMPLETE_DEALLOCATOR. This is
> clearly a false positive, but we still want to get rid of this
> warning.
> 
> We now register the execution context in global area so that
> passt_exit() can use it to close these descriptors before calling
> _exit().  All exit paths (signal handler, die(), die_perror())
> funnel through passt_exit(), so this covers all cases.
> 
> Signed-off-by: Jon Maloy <jmaloy@redhat.com>
> 
> ---
> v2: - Made struct ctx global from the beginning, on suggestion
>       from David Gibson.
>     - Drop pidfile_fd from passt_exit() cleanup, since it can be
>       closed directly after use.
> 
> Signed-off-by: Jon Maloy <jmaloy@redhat.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

Although one tiny nit..

> ---
>  passt.c | 77 +++++++++++++++++++++++++++++++--------------------------
>  passt.h |  2 ++
>  util.c  |  7 ++++++
>  3 files changed, 51 insertions(+), 35 deletions(-)
> 
> diff --git a/passt.c b/passt.c
> index b3f806b9..e75b80b1 100644
> --- a/passt.c
> +++ b/passt.c
> @@ -62,6 +62,13 @@
>  
>  char pkt_buf[PKT_BUF_BYTES]	__attribute__ ((aligned(PAGE_SIZE)));
>  
> +struct ctx passt_ctx = {
> +	.pidfile_fd		= -1,
> +	.fd_tap			= -1,
> +	.pasta_netns_fd		= -1,
> +	.device_state_fd	= -1,
> +};
> +
>  char *epoll_type_str[] = {
>  	[EPOLL_TYPE_TCP]		= "connected TCP socket",
>  	[EPOLL_TYPE_TCP_SPLICE]		= "connected spliced TCP socket",
> @@ -322,9 +329,9 @@ static void passt_worker(void *opaque, int nfds, struct epoll_event *events)
>   */
>  int main(int argc, char **argv)
>  {
> +	struct ctx *c = &passt_ctx;

.. this line belongs one below according to our reverse christmas tree convention.


>  	struct epoll_event events[NUM_EPOLL_EVENTS];
>  	int nfds, devnull_fd = -1;
> -	struct ctx c = { 0 };
>  	struct rlimit limit;
>  	struct timespec now;
>  	struct sigaction sa;
> @@ -336,18 +343,15 @@ int main(int argc, char **argv)
>  
>  	isolate_initial(argc, argv);
>  
> -	c.pasta_netns_fd = c.fd_tap = c.pidfile_fd = -1;
> -	c.device_state_fd = -1;
> -
>  	sigemptyset(&sa.sa_mask);
>  	sa.sa_flags = 0;
>  	sa.sa_handler = exit_handler;
>  	sigaction(SIGTERM, &sa, NULL);
>  	sigaction(SIGQUIT, &sa, NULL);
>  
> -	c.mode = conf_mode(argc, argv);
> +	c->mode = conf_mode(argc, argv);
>  
> -	if (c.mode == MODE_PASTA) {
> +	if (c->mode == MODE_PASTA) {
>  		sa.sa_handler = pasta_child_handler;
>  		if (sigaction(SIGCHLD, &sa, NULL))
>  			die_perror("Couldn't install signal handlers");
> @@ -358,67 +362,70 @@ int main(int argc, char **argv)
>  
>  	madvise(pkt_buf, sizeof(pkt_buf), MADV_HUGEPAGE);
>  
> -	c.epollfd = epoll_create1(EPOLL_CLOEXEC);
> -	if (c.epollfd == -1)
> +	c->epollfd = epoll_create1(EPOLL_CLOEXEC);
> +	if (c->epollfd == -1)
>  		die_perror("Failed to create epoll file descriptor");
> -	flow_epollid_register(EPOLLFD_ID_DEFAULT, c.epollfd);
> +	flow_epollid_register(EPOLLFD_ID_DEFAULT, c->epollfd);
>  
>  	if (getrlimit(RLIMIT_NOFILE, &limit))
>  		die_perror("Failed to get maximum value of open files limit");
>  
> -	c.nofile = limit.rlim_cur = limit.rlim_max;
> +	c->nofile = limit.rlim_cur = limit.rlim_max;
>  	if (setrlimit(RLIMIT_NOFILE, &limit))
>  		die_perror("Failed to set current limit for open files");
>  
> -	sock_probe_features(&c);
> +	sock_probe_features(c);
>  
> -	conf(&c, argc, argv);
> -	trace_init(c.trace);
> +	conf(c, argc, argv);
> +	trace_init(c->trace);
>  
> -	pasta_netns_quit_init(&c);
> +	pasta_netns_quit_init(c);
>  
> -	tap_backend_init(&c);
> +	tap_backend_init(c);
>  
> -	random_init(&c);
> +	random_init(c);
>  
>  	if (clock_gettime(CLOCK_MONOTONIC, &now))
>  		die_perror("Failed to get CLOCK_MONOTONIC time");
>  
>  	flow_init();
> -	fwd_scan_ports_init(&c);
> +	fwd_scan_ports_init(c);
>  
> -	if ((!c.no_udp && udp_init(&c)) || (!c.no_tcp && tcp_init(&c)))
> +	if ((!c->no_udp && udp_init(c)) || (!c->no_tcp && tcp_init(c)))
>  		passt_exit(EXIT_FAILURE);
>  
> -	if (fwd_listen_init(&c))
> +	if (fwd_listen_init(c))
>  		passt_exit(EXIT_FAILURE);
>  
> -	proto_update_l2_buf(c.guest_mac);
> +	proto_update_l2_buf(c->guest_mac);
>  
> -	if (c.ifi4 && !c.no_dhcp)
> +	if (c->ifi4 && !c->no_dhcp)
>  		dhcp_init();
>  
> -	if (c.ifi6 && !c.no_dhcpv6)
> -		dhcpv6_init(&c);
> +	if (c->ifi6 && !c->no_dhcpv6)
> +		dhcpv6_init(c);
>  
> -	pcap_init(&c);
> +	pcap_init(c);
>  
> -	fwd_neigh_table_init(&c);
> -	nl_neigh_notify_init(&c);
> +	fwd_neigh_table_init(c);
> +	nl_neigh_notify_init(c);
>  
> -	if (!c.foreground) {
> +	if (!c->foreground) {
>  		if ((devnull_fd = open("/dev/null", O_RDWR | O_CLOEXEC)) < 0)
>  			die_perror("Failed to open /dev/null");
>  	}
>  
> -	if (isolate_prefork(&c))
> +	if (isolate_prefork(c))
>  		die("Failed to sandbox process, exiting");
>  
> -	if (!c.foreground) {
> -		__daemon(c.pidfile_fd, devnull_fd);
> +	if (!c->foreground) {
> +		__daemon(c->pidfile_fd, devnull_fd);
> +		close(c->pidfile_fd);
> +		c->pidfile_fd = -1;
>  		log_stderr = false;
>  	} else {
> -		pidfile_write(c.pidfile_fd, getpid());
> +		pidfile_write(c->pidfile_fd, getpid());
> +		c->pidfile_fd = -1;
>  	}
>  
>  	if (pasta_child_pid) {
> @@ -426,19 +433,19 @@ int main(int argc, char **argv)
>  		log_stderr = false;
>  	}
>  
> -	isolate_postfork(&c);
> +	isolate_postfork(c);
>  
> -	timer_init(&c, &now);
> +	timer_init(c, &now);
>  
>  loop:
>  	/* NOLINTBEGIN(bugprone-branch-clone): intervals can be the same */
>  	/* cppcheck-suppress [duplicateValueTernary, unmatchedSuppression] */
> -	nfds = epoll_wait(c.epollfd, events, NUM_EPOLL_EVENTS, TIMER_INTERVAL);
> +	nfds = epoll_wait(c->epollfd, events, NUM_EPOLL_EVENTS, TIMER_INTERVAL);
>  	/* NOLINTEND(bugprone-branch-clone) */
>  	if (nfds == -1 && errno != EINTR)
>  		die_perror("epoll_wait() failed in main loop");
>  
> -	passt_worker(&c, nfds, events);
> +	passt_worker(c, nfds, events);
>  
>  	goto loop;
>  }
> diff --git a/passt.h b/passt.h
> index 1726965d..e1905f4c 100644
> --- a/passt.h
> +++ b/passt.h
> @@ -307,6 +307,8 @@ struct ctx {
>  	bool migrate_exit;
>  };
>  
> +extern struct ctx passt_ctx;
> +
>  void proto_update_l2_buf(const unsigned char *eth_d);
>  
>  #endif /* PASST_H */
> diff --git a/util.c b/util.c
> index b64c29ed..ef6ba80e 100644
> --- a/util.c
> +++ b/util.c
> @@ -1108,6 +1108,13 @@ void abort_with_msg(const char *fmt, ...)
>   */
>  void passt_exit(int status)
>  {
> +	if (passt_ctx.fd_tap_listen >= 0)
> +		close(passt_ctx.fd_tap_listen);
> +	if (passt_ctx.fd_repair_listen >= 0)
> +		close(passt_ctx.fd_repair_listen);
> +	if (passt_ctx.fd_control_listen >= 0)
> +		close(passt_ctx.fd_control_listen);
> +
>  	/* Make sure we don't leave the pcap file truncated */
>  	if (pcap_fd != -1 && fsync(pcap_fd))
>  		warn_perror("Failed to flush pcap file, it might be truncated");
> -- 
> 2.52.0
> 
> 

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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