From: Yun-Hao Chung <howardchung@xxxxxxxxxxxx>
When channel_free is called and we are waiting for a command response
from the peer, bluez NULL the setup->session but would not free its
setup_cb. Since setup_cb holds a ref of setup, the setup wouldn't be
freed and if service_removed is called after channel_free, a2dp_cancel
tries to abort the ongoing avdtp commands, which accesses the
setup->session and triggers a crash.
This change finalizes all avdtp commands before assigning setup->session
to NULL in channel_free.
Crash stack trace:
0x000059f01943e688 (bluetoothd -avdtp.c:3690)
avdtp_abort
0x000059f01943928a (bluetoothd -a2dp.c:3069)
a2dp_cancel
0x000059f0194377fa (bluetoothd -sink.c:324)
sink_unregister
0x000059f01948715a (bluetoothd -service.c:177)
service_remove
0x000059f01948d77c (bluetoothd -device.c:5346)
device_remove
0x000059f019476d14 (bluetoothd -adapter.c:7202)
adapter_remove
0x000059f019476c3e (bluetoothd -adapter.c:10827)
adapter_cleanup
0x000059f01949d8d7 (bluetoothd -main.c:1114) main
0x0000787b36185d74 (libc.so.6 -libc-start.c:308)
__libc_start_main
0x000059f019433e39 (bluetoothd + 0x00026e39) _start
0x00007fff2d2c0127
Reviewed-by: Archie Pusaka <apusaka@xxxxxxxxxxxx>
---
There are two other options to fix this crash.
1. add a NULL check in a2dp_cancel before calling avdtp_abort.
2. call setup_cb_free to every setup_cb in setup->cb in channel_free.
Since each setup_cb needs setup->session, I think there is no need to
keep the setup_cb after assigning setup->session to NULL. So the first
option is not ideal. If the second option is adopted, there would be
some time that sink/source->connect_id/disconnect_id is not zero, but
there is no corresponding setup_cb.
Test steps:
Reproduce the crash with the following steps. Verify the crash is
no longer observed after this change.
1. ignore AVDTP_SET_CONFIGURATION resp by modifying avdtp.c
2. turn on a paired headset
3. check the bluetooth.log, while bluez is waiting for
AVDTP_SET_CONFIGURATION resp, stop bluetoothd immediately.
This will trigger:
session_cb (I/O error) -> connection_lost
-> avdtp_set_state (AVDTP_SESSION_STATE_DISCONNECTED)
-> avdtp_state_cb -> channel_remove -> channel_free
then:
adapter_cleanup -> adapter_remove -> device_remove -> service_remove
-> a2dp_sink_remove -> sink_unregister -> sink_free -> a2dp_cancel
4. check if bluetoothd crash
The above steps can trigger the crash 100%.
Changes in v3:
- Remove the duplicated finalize_all
Changes in v2:
- Implement helper function finalize_all
- add setup_ref before finalize_all, in case the setup is freed during
finalize
profiles/audio/a2dp.c | 37 ++++++++++++++++++++++++++++++++++++-
1 file changed, 36 insertions(+), 1 deletion(-)
diff --git a/profiles/audio/a2dp.c b/profiles/audio/a2dp.c
index d31ed845cbe7..39d5e3ef736c 100644
--- a/profiles/audio/a2dp.c
+++ b/profiles/audio/a2dp.c
@@ -404,6 +404,38 @@ static void finalize_discover(struct a2dp_setup *s)
}
}
+static void finalize_all(struct a2dp_setup *s)
+{
+ GSList *l;
+ struct avdtp_stream *stream = s->err ? NULL : s->stream;
+
+ for (l = s->cb; l != NULL; ) {
+ struct a2dp_setup_cb *cb = l->data;
+
+ l = l->next;
+
+ if (cb->discover_cb) {
+ cb->discover_cb(s->session, s->seps,
+ error_to_errno(s->err), cb->user_data);
+ } else if (cb->select_cb) {
+ cb->select_cb(s->session, s->seps, s->caps,
+ error_to_errno(s->err), cb->user_data);
+ } else if (cb->suspend_cb) {
+ cb->suspend_cb(s->session,
+ error_to_errno(s->err), cb->user_data);
+ } else if (cb->resume_cb) {
+ cb->resume_cb(s->session,
+ error_to_errno(s->err), cb->user_data);
+ } else if (cb->config_cb) {
+ cb->config_cb(s->session, s->seps, stream,
+ error_to_errno(s->err), cb->user_data);
+ } else
+ warn("setup_cb doesn't have any callback function");
+
+ setup_cb_free(cb);
+ }
+}
+
static struct a2dp_setup *find_setup_by_session(struct avdtp *session)
{
GSList *l;
@@ -1540,9 +1572,12 @@ static void channel_free(void *data)
setup = find_setup_by_session(chan->session);
if (setup) {
setup->chan = NULL;
+ setup_ref(setup);
+ /* Finalize pending commands before we NULL setup->session */
+ finalize_setup_errno(setup, -ENOTCONN, finalize_all, NULL);
avdtp_unref(setup->session);
setup->session = NULL;
- finalize_setup_errno(setup, -ENOTCONN, NULL);
+ setup_unref(setup);
}
g_free(chan);
--
2.32.0.93.g670b81a890-goog
