[pulseaudio-discuss] [PATCH] bluetooth: Fix crash when disabling Bluetooth adapter

[Frédéric Danis]

This crash occurs when PA is connected to a phone through the oFono
backend.
When disabling the Bluetooth adapter, pa_bluetooth_device is removed before
hf_audio_card. Both keep refs on pa_bluetooth_transport. Those removal will
call pa_bluetooth_transport_free() from device_free() (bluez5-util.c) and
hf_audio_card_free() (backend-ofono.c).
In the end, the call to pa_bluetooth_transport_free() calls
pa_hasmap_remove() through pa_bluetooth_transport_unlink(), but since
memory has already been freed, the second try results in a segfault.

Triggering hf_audio_card removal during pa_bluetooth_device removal allows
hf_audio_card to be freed at the right time.
---
 src/modules/bluetooth/backend-ofono.c | 18 ++++++++++++++++++
 src/modules/bluetooth/bluez5-util.c   |  2 ++
 src/modules/bluetooth/bluez5-util.h   |  1 +
 3 files changed, 21 insertions(+)

diff --git a/src/modules/bluetooth/backend-ofono.c b/src/modules/bluetooth/backend-ofono.c
index 1f0efe923..0e5bbe8b7 100644
--- a/src/modules/bluetooth/backend-ofono.c
+++ b/src/modules/bluetooth/backend-ofono.c
@@ -70,6 +70,7 @@ struct hf_audio_card {
     int (*acquire)(struct hf_audio_card *card);
 
     pa_bluetooth_transport *transport;
+    pa_hook_slot *device_unlink_slot;
 };
 
 struct pa_bluetooth_backend {
@@ -181,6 +182,17 @@ static int card_acquire(struct hf_audio_card *card) {
     return -1;
 }
 
+static void hf_audio_agent_card_removed(pa_bluetooth_backend *backend, const char *path);
+
+static pa_hook_result_t device_unlink_cb(pa_bluetooth_discovery *y, const pa_bluetooth_device *d, struct hf_audio_card *card) {
+    pa_assert(d);
+    pa_assert(card);
+
+    hf_audio_agent_card_removed(card->backend, card->path);
+
+    return PA_HOOK_OK;
+}
+
 static struct hf_audio_card *hf_audio_card_new(pa_bluetooth_backend *backend, const char *path) {
     struct hf_audio_card *card = pa_xnew0(struct hf_audio_card, 1);
 
@@ -189,12 +201,18 @@ static struct hf_audio_card *hf_audio_card_new(pa_bluetooth_backend *backend, co
     card->fd = -1;
     card->acquire = card_acquire;
 
+    card->device_unlink_slot = pa_hook_connect(pa_bluetooth_discovery_hook(backend->discovery, PA_BLUETOOTH_HOOK_DEVICE_UNLINK),
+                                               PA_HOOK_NORMAL, (pa_hook_cb_t) device_unlink_cb, card);
+
     return card;
 }
 
 static void hf_audio_card_free(struct hf_audio_card *card) {
     pa_assert(card);
 
+    if (card->device_unlink_slot)
+        pa_hook_slot_free(card->device_unlink_slot);
+
     if (card->transport)
         pa_bluetooth_transport_free(card->transport);
 
diff --git a/src/modules/bluetooth/bluez5-util.c b/src/modules/bluetooth/bluez5-util.c
index 3c5a000c0..d95c9c117 100644
--- a/src/modules/bluetooth/bluez5-util.c
+++ b/src/modules/bluetooth/bluez5-util.c
@@ -562,6 +562,8 @@ static void device_free(pa_bluetooth_device *d) {
 
     device_stop_waiting_for_profiles(d);
 
+    pa_hook_fire(&d->discovery->hooks[PA_BLUETOOTH_HOOK_DEVICE_UNLINK], d);
+
     for (i = 0; i < PA_BLUETOOTH_PROFILE_COUNT; i++) {
         pa_bluetooth_transport *t;
 
diff --git a/src/modules/bluetooth/bluez5-util.h b/src/modules/bluetooth/bluez5-util.h
index 82739bffd..1e9caecb4 100644
--- a/src/modules/bluetooth/bluez5-util.h
+++ b/src/modules/bluetooth/bluez5-util.h
@@ -50,6 +50,7 @@ typedef enum pa_bluetooth_hook {
     PA_BLUETOOTH_HOOK_TRANSPORT_STATE_CHANGED,            /* Call data: pa_bluetooth_transport */
     PA_BLUETOOTH_HOOK_TRANSPORT_MICROPHONE_GAIN_CHANGED,  /* Call data: pa_bluetooth_transport */
     PA_BLUETOOTH_HOOK_TRANSPORT_SPEAKER_GAIN_CHANGED,     /* Call data: pa_bluetooth_transport */
+    PA_BLUETOOTH_HOOK_DEVICE_UNLINK,                      /* Call data: pa_bluetooth_device */
     PA_BLUETOOTH_HOOK_MAX
 } pa_bluetooth_hook_t;
 
-- 
2.18.0