| Message ID | 20210712203813.Bluez.v1.1.Id7aa1152377161d17b442bf258773d9b6c624ca3@changeid |
|---|---|
| State | New |
| Headers | show |
| Series | [Bluez,v1] a2dp: Fix crash in channel_free while waiting cmd resp | expand |
Hi Howard, On Mon, Jul 12, 2021 at 5:39 AM Howard Chung <howardchung@google.com> wrote: > > From: Yun-Hao Chung <howardchung@chromium.org> > > 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@chromium.org> > --- > 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%. > > profiles/audio/a2dp.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/profiles/audio/a2dp.c b/profiles/audio/a2dp.c > index d31ed845cbe7..f201b98c79d0 100644 > --- a/profiles/audio/a2dp.c > +++ b/profiles/audio/a2dp.c > @@ -1540,9 +1540,14 @@ static void channel_free(void *data) > setup = find_setup_by_session(chan->session); > if (setup) { > setup->chan = NULL; > + /* Finalize pending commands before we NULL setup->session */ > + finalize_setup_errno(setup, -ENOTCONN, finalize_discover, > + finalize_select, > + finalize_config, > + finalize_resume, > + finalize_suspend, NULL); While the analysis seems correct I wonder if wouldn't be a better idea to have a finalize_all so we don't have to iterate the callback list multiple times, other than that the patch looks good and I would prioritize it to have it included asap. > avdtp_unref(setup->session); > setup->session = NULL; > - finalize_setup_errno(setup, -ENOTCONN, NULL); > } > > g_free(chan); > -- > 2.32.0.93.g670b81a890-goog >
diff --git a/profiles/audio/a2dp.c b/profiles/audio/a2dp.c index d31ed845cbe7..f201b98c79d0 100644 --- a/profiles/audio/a2dp.c +++ b/profiles/audio/a2dp.c @@ -1540,9 +1540,14 @@ static void channel_free(void *data) setup = find_setup_by_session(chan->session); if (setup) { setup->chan = NULL; + /* Finalize pending commands before we NULL setup->session */ + finalize_setup_errno(setup, -ENOTCONN, finalize_discover, + finalize_select, + finalize_config, + finalize_resume, + finalize_suspend, NULL); avdtp_unref(setup->session); setup->session = NULL; - finalize_setup_errno(setup, -ENOTCONN, NULL); } g_free(chan);