2022-03-08 12:44:08

by Yun-hao Chung

[permalink] [raw]
Subject: [Bluez PATCH v2] audio: fix crash in a2dp_discover

From: Yun-Hao Chung <[email protected]>

Sample stack trace:
0x0000567c394e4c6b (bluetoothd - a2dp.c: 270) setup_cb_free
0x0000567c394e4a94 (bluetoothd - a2dp.c: 2884) a2dp_discover
0x0000567c394e3c03 (bluetoothd - sink.c: 275) sink_setup_stream
0x0000567c394e3d4f (bluetoothd - sink.c: 299) sink_connect
0x0000567c39535183 (bluetoothd - service.c: 294) btd_service_connect
0x0000567c39539f68 (bluetoothd - device.c: 2006) connect_next
0x0000567c3954086d (bluetoothd - device.c: 2060) service_state_changed
0x0000567c39534efb (bluetoothd - service.c: 111) change_state
0x0000567c3953559c (bluetoothd - service.c: 0)
btd_service_connecting_complete
0x0000567c39534a5c (bluetoothd - profile.c: 1641) record_cb
0x0000567c395197cd (bluetoothd - sdp-client.c: 298) connect_watch
0x00007b14bc8034f6 (libglib-2.0.so.0 - gmain.c: 3337)
g_main_context_dispatch
0x00007b14bc803801 (libglib-2.0.so.0 - gmain.c: 4131)
g_main_context_iterate
0x00007b14bc803a7d (libglib-2.0.so.0 - gmain.c: 4329) g_main_loop_run
0x0000567c39566af1 (bluetoothd - mainloop-glib.c: 79) mainloop_run
0x0000567c39566ddb (bluetoothd - mainloop-notify.c: 201)
mainloop_run_with_signal
0x0000567c3954bf4c (bluetoothd - main.c: 1222) main
0x00007b14bc579797 (libc.so.6 - libc-start.c: 332) __libc_start_main
0x0000567c394df449 (bluetoothd) _start
0x00007ffd70145737

This could be triggered from a2dp_discover -> avdtp_discover ->
send_request -> send_req -> l2cap_connect (return error) ->
avdtp_set_state (to disconnect state)-> channel_remove -> channel_free
-> finalize_setup_errno (discover cb is freed) -> error handling all
the way back to a2dp_discover -> a2dp_discover (discover cb is freed
again, crashed!).

The fix is to attach cb with setup after avdtp_discover success.

Suggested-by: [email protected]

Reviewed-by: Archie Pusaka <[email protected]>
---
Hi maintainers,

The fix is tested by forcing session->io to NULL in send_req in the code
and verifing the crash doesn't happen.

Changes in v2:
- adopted luiz's solution

profiles/audio/a2dp.c | 26 ++++++++++++++++++++------
1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/profiles/audio/a2dp.c b/profiles/audio/a2dp.c
index 9fbcd35f7..f761dbe54 100644
--- a/profiles/audio/a2dp.c
+++ b/profiles/audio/a2dp.c
@@ -244,6 +244,15 @@ static struct a2dp_setup_cb *setup_cb_new(struct a2dp_setup *setup)
cb->setup = setup;
cb->id = ++cb_id;

+ return cb;
+}
+
+static struct a2dp_setup_cb *setup_cb_add(struct a2dp_setup *setup)
+{
+ struct a2dp_setup_cb *cb;
+
+ cb = setup_cb_new(setup);
+
setup->cb = g_slist_append(setup->cb, cb);
return cb;
}
@@ -1840,7 +1849,7 @@ static int a2dp_reconfig(struct a2dp_channel *chan, const char *sender,
if (!setup)
return -ENOMEM;

- cb_data = setup_cb_new(setup);
+ cb_data = setup_cb_add(setup);
cb_data->config_cb = reconfig_cb;
cb_data->user_data = user_data;

@@ -2878,12 +2887,17 @@ unsigned int a2dp_discover(struct avdtp *session, a2dp_discover_cb_t cb,
if (!setup)
return 0;

+ /* Don't add cb since avdtp_discover can end up disconnecting the
+ * session causing the cb to be freed.
+ */
cb_data = setup_cb_new(setup);
cb_data->discover_cb = cb;
cb_data->user_data = user_data;

- if (avdtp_discover(session, discover_cb, setup) == 0)
+ if (avdtp_discover(session, discover_cb, setup) == 0) {
+ setup->cb = g_slist_append(setup->cb, cb_data);
return cb_data->id;
+ }

setup_cb_free(cb_data);
return 0;
@@ -2911,7 +2925,7 @@ unsigned int a2dp_select_capabilities(struct avdtp *session,
if (!setup)
return 0;

- cb_data = setup_cb_new(setup);
+ cb_data = setup_cb_add(setup);
cb_data->select_cb = cb;
cb_data->user_data = user_data;

@@ -2984,7 +2998,7 @@ unsigned int a2dp_config(struct avdtp *session, struct a2dp_sep *sep,
if (!setup)
return 0;

- cb_data = setup_cb_new(setup);
+ cb_data = setup_cb_add(setup);
cb_data->config_cb = cb;
cb_data->user_data = user_data;

@@ -3075,7 +3089,7 @@ unsigned int a2dp_resume(struct avdtp *session, struct a2dp_sep *sep,
if (!setup)
return 0;

- cb_data = setup_cb_new(setup);
+ cb_data = setup_cb_add(setup);
cb_data->resume_cb = cb;
cb_data->user_data = user_data;

@@ -3133,7 +3147,7 @@ unsigned int a2dp_suspend(struct avdtp *session, struct a2dp_sep *sep,
if (!setup)
return 0;

- cb_data = setup_cb_new(setup);
+ cb_data = setup_cb_add(setup);
cb_data->suspend_cb = cb;
cb_data->user_data = user_data;

--
2.35.1.616.g0bdcbb4464-goog


2022-03-08 23:37:40

by bluez.test.bot

[permalink] [raw]
Subject: RE: [Bluez,v2] audio: fix crash in a2dp_discover

This is automated email and please do not reply to this email!

Dear submitter,

Thank you for submitting the patches to the linux bluetooth mailing list.
This is a CI test results with your patch series:
PW Link:https://patchwork.kernel.org/project/bluetooth/list/?series=621407

---Test result---

Test Summary:
CheckPatch PASS 1.57 seconds
GitLint PASS 1.06 seconds
Prep - Setup ELL PASS 43.82 seconds
Build - Prep PASS 0.71 seconds
Build - Configure PASS 8.66 seconds
Build - Make PASS 1737.37 seconds
Make Check PASS 11.41 seconds
Make Check w/Valgrind PASS 459.80 seconds
Make Distcheck PASS 248.64 seconds
Build w/ext ELL - Configure PASS 9.35 seconds
Build w/ext ELL - Make PASS 1311.54 seconds
Incremental Build with patchesPASS 0.00 seconds



---
Regards,
Linux Bluetooth