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sd-bus: fix exiting event loop when sd_bus_set_exit_on_disconnect is used

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If sd_bus_set_exit_on_disconnect is used and the bus is part of an event
loop, and the D-Bus connection goes away (e.g.: soft-reboot), sd-bus
will always exit() the program instead of returning from the loop, as
the reference to the event is removed before it is checked.
This commit is contained in:
Luca Boccassi 2024-01-25 20:31:39 +00:00 committed by Daan De Meyer
parent 9b8dd5fbea
commit b5d4862707
2 changed files with 20 additions and 7 deletions
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18
src/libsystemd/sd-bus/sd-bus.c
View File

@ -3087,7 +3087,7 @@ null_message:
return r;
}
static int bus_exit_now(sd_bus *bus) {
static int bus_exit_now(sd_bus *bus, sd_event *event) {
assert(bus);
/* Exit due to close, if this is requested. If this is bus object is attached to an event source, invokes
@ -3104,8 +3104,11 @@ static int bus_exit_now(sd_bus *bus) {
log_debug("Bus connection disconnected, exiting.");
if (bus->event)
return sd_event_exit(bus->event, EXIT_FAILURE);
if (!event)
event = bus->event;
if (event)
return sd_event_exit(event, EXIT_FAILURE);
else
exit(EXIT_FAILURE);
@ -3167,6 +3170,7 @@ static int process_closing_reply_callback(sd_bus *bus, struct reply_callback *c)
static int process_closing(sd_bus *bus, sd_bus_message **ret) {
_cleanup_(sd_bus_message_unrefp) sd_bus_message *m = NULL;
_cleanup_(sd_event_unrefp) sd_event *event = NULL;
struct reply_callback *c;
int r;
@ -3201,6 +3205,10 @@ static int process_closing(sd_bus *bus, sd_bus_message **ret) {
if (r < 0)
return r;
/* sd_bus_close() will deref the event and set bus->event to NULL. But in bus_exit_now() we use
* bus->event to decide whether to return from the event loop or exit(), but given it's always NULL
* at that point, it always exit(). Ref it here and pass it through further down to avoid that. */
event = sd_event_ref(bus->event);
sd_bus_close(bus);
bus->current_message = m;
@ -3216,7 +3224,7 @@ static int process_closing(sd_bus *bus, sd_bus_message **ret) {
/* Nothing else to do, exit now, if the condition holds */
bus->exit_triggered = true;
(void) bus_exit_now(bus);
(void) bus_exit_now(bus, event);
if (ret)
*ret = TAKE_PTR(m);
@ -4312,7 +4320,7 @@ _public_ int sd_bus_set_exit_on_disconnect(sd_bus *bus, int b) {
bus->exit_on_disconnect = b;
/* If the exit condition was triggered already, exit immediately. */
return bus_exit_now(bus);
return bus_exit_now(bus, /* event= */ NULL);
}
_public_ int sd_bus_get_exit_on_disconnect(sd_bus *bus) {

9
src/libsystemd/sd-bus/test-bus-watch-bind.c
View File

@ -7,6 +7,7 @@
#include "sd-id128.h"
#include "alloc-util.h"
#include "bus-internal.h"
#include "fd-util.h"
#include "fs-util.h"
#include "mkdir.h"
@ -27,8 +28,11 @@ static int method_foobar(sd_bus_message *m, void *userdata, sd_bus_error *ret_er
static int method_exit(sd_bus_message *m, void *userdata, sd_bus_error *ret_error) {
log_info("Got Exit() call");
assert_se(sd_event_exit(sd_bus_get_event(sd_bus_message_get_bus(m)), 1) >= 0);
return sd_bus_reply_method_return(m, NULL);
assert_se(sd_bus_reply_method_return(m, NULL) >= 0);
/* Simulate D-Bus going away to test the bus_exit_now() path with exit_on_disconnect set */
bus_enter_closing(sd_bus_message_get_bus(m));
return 0;
}
static const sd_bus_vtable vtable[] = {
@ -100,6 +104,7 @@ static void* thread_server(void *p) {
log_debug("Accepted server connection");
assert_se(sd_bus_new(&bus) >= 0);
assert_se(sd_bus_set_exit_on_disconnect(bus, true) >= 0);
assert_se(sd_bus_set_description(bus, "server") >= 0);
assert_se(sd_bus_set_fd(bus, bus_fd, bus_fd) >= 0);
assert_se(sd_bus_set_server(bus, true, id) >= 0);