[PATCH] gatt-client: avoid UAF after acquire notify failure

[PATCH] gatt-client: avoid UAF after acquire notify failure

[Andreas Kemnade]

If a disconnect happens during AcquireNotify dbus calls, a lot of
debris is left over. Subsequent calls to AcquireNotify will return
NotPermitted and StopNotify leads to an UAF, crashing bluetoothd.

Fix that by also clean up the socket stuff on failure.

This was provoked by putting the device into some RF shielding bag
and open and close it quickly.

Valgrind output:

bluetoothd[26032]: [:1.126:method_call] > org.bluez.GattCharacteristic1.AcquireNotify [#145]
bluetoothd[26032]: [:1.126:error] < org.bluez.Error.NotPermitted [#145]
bluetoothd[26032]: [:1.74:method_call] > org.freedesktop.DBus.Properties.GetAll [#895]
bluetoothd[26032]: [:1.74:method_return] < [#895]
bluetoothd[26032]: [:1.74:method_call] > org.bluez.GattCharacteristic1.StopNotify [#896]
==26032== Invalid read of size 8
==26032==    at 0x1A5721: notify_io_destroy (gatt-client.c:1562)
==26032==    by 0x1A7290: sock_io_destroy (gatt-client.c:1171)
==26032==    by 0x1A7290: destroy_sock (gatt-client.c:1192)
==26032==    by 0x1A73D6: characteristic_stop_notify (gatt-client.c:1698)
==26032==    by 0x1CF478: process_message (object.c:293)
==26032==    by 0x49CB71B: ??? (in /usr/lib/x86_64-linux-gnu/libdbus-1.so.3.32.4)
==26032==    by 0x49BB62A: dbus_connection_dispatch (in /usr/lib/x86_64-linux-gnu/libdbus-1.so.3.32.4)
==26032==    by 0x1CBCEF: message_dispatch (mainloop.c:59)
==26032==    by 0x48BF61E: g_main_context_dispatch (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.7400.6)
==26032==    by 0x48BF9D7: ??? (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.7400.6)
==26032==    by 0x48BFC8E: g_main_loop_run (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.7400.6)
==26032==    by 0x202114: mainloop_run (mainloop-glib.c:65)
==26032==    by 0x202501: mainloop_run_with_signal (mainloop-notify.c:196)
==26032==  Address 0x5a7a430 is 0 bytes inside a block of size 32 free'd
==26032==    at 0x484417B: free (vg_replace_malloc.c:872)
==26032==    by 0x1DEC0F: complete_notify_request (gatt-client.c:1663)
==26032==    by 0x1DEC0F: enable_ccc_callback (gatt-client.c:1735)
==26032==    by 0x1DB8FF: disc_att_send_op (att.c:464)
==26032==    by 0x1DB8FF: disconnect_cb (att.c:676)
==26032==    by 0x2017A4: watch_callback (io-glib.c:173)
==26032==    by 0x48BF61E: g_main_context_dispatch (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.7400.6)
==26032==    by 0x48BF9D7: ??? (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.7400.6)
==26032==    by 0x48BFC8E: g_main_loop_run (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.7400.6)
==26032==    by 0x202114: mainloop_run (mainloop-glib.c:65)
==26032==    by 0x202501: mainloop_run_with_signal (mainloop-notify.c:196)
==26032==    by 0x12E60C: main (main.c:1535)
==26032==  Block was alloc'd at
==26032==    at 0x48417B4: malloc (vg_replace_malloc.c:381)
==26032==    by 0x1D2F4D: util_malloc (util.c:46)
==26032==    by 0x1A5DD3: notify_client_create (gatt-client.c:1426)
==26032==    by 0x1A5EFC: characteristic_acquire_notify (gatt-client.c:1588)
==26032==    by 0x1CF478: process_message (object.c:293)
==26032==    by 0x49CB71B: ??? (in /usr/lib/x86_64-linux-gnu/libdbus-1.so.3.32.4)
==26032==    by 0x49BB62A: dbus_connection_dispatch (in /usr/lib/x86_64-linux-gnu/libdbus-1.so.3.32.4)
==26032==    by 0x1CBCEF: message_dispatch (mainloop.c:59)
==26032==    by 0x48BF61E: g_main_context_dispatch (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.7400.6)
==26032==    by 0x48BF9D7: ??? (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.7400.6)
---
 src/gatt-client.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/gatt-client.c b/src/gatt-client.c
index 3c31a422e..a146d52cb 100644
--- a/src/gatt-client.c
+++ b/src/gatt-client.c
@@ -1539,8 +1539,7 @@ static void register_notify_io_cb(uint16_t att_ecode, void *user_data)
 	struct bt_gatt_client *gatt = chrc->service->client->gatt;
 
 	if (att_ecode) {
-		queue_remove(chrc->notify_clients, client);
-		notify_client_free(client);
+		destroy_sock(chrc, chrc->notify_io->io);
 		return;
 	}
 
-- 
2.39.5

RE: gatt-client: avoid UAF after acquire notify failure

[bluez.test.bot]

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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=975818

---Test result---

Test Summary:
CheckPatch                    PENDING   0.34 seconds
GitLint                       PENDING   0.26 seconds
BuildEll                      PASS      21.42 seconds
BluezMake                     PASS      3050.39 seconds
MakeCheck                     PASS      20.88 seconds
MakeDistcheck                 PASS      214.61 seconds
CheckValgrind                 PASS      292.86 seconds
CheckSmatch                   PASS      315.51 seconds
bluezmakeextell               PASS      129.49 seconds
IncrementalBuild              PENDING   0.25 seconds
ScanBuild                     PASS      926.90 seconds

Details
##############################
Test: CheckPatch - PENDING
Desc: Run checkpatch.pl script
Output:

##############################
Test: GitLint - PENDING
Desc: Run gitlint
Output:

##############################
Test: IncrementalBuild - PENDING
Desc: Incremental build with the patches in the series
Output:



---
Regards,
Linux Bluetooth

Re: [PATCH] gatt-client: avoid UAF after acquire notify failure

[Andreas Kemnade]

Am Wed, 25 Jun 2025 16:05:45 +0200
schrieb Andreas Kemnade <andreas@kemnade.info>:

> If a disconnect happens during AcquireNotify dbus calls, a lot of
> debris is left over. Subsequent calls to AcquireNotify will return
> NotPermitted and StopNotify leads to an UAF, crashing bluetoothd.
> 
> Fix that by also clean up the socket stuff on failure.
> 
Hmm, I should rather send a dbus answer, too instead of letting the app
waiting for timeout.
I will send an extended version (then with the correct subj prefix)

Regards,
Andreas