[PATCH v4] Bluetooth: hci_conn: fix potential UAF in create_big_sync

[PATCH v4] Bluetooth: hci_conn: fix potential UAF in create_big_sync

[David Carlier]

Add hci_conn_valid() check in create_big_sync() to detect stale
connections before proceeding with BIG creation. Handle the
resulting -ECANCELED in create_big_complete() and re-validate the
connection under hci_dev_lock() before dereferencing, matching the
pattern used by create_le_conn_complete() and create_pa_complete().

Keep the hci_conn object alive across the async boundary by taking
a reference via hci_conn_get() when queueing create_big_sync(), and
dropping it in the completion callback. The refcount and the lock
are complementary: the refcount keeps the object allocated, while
hci_dev_lock() serializes hci_conn_hash_del()'s list_del_rcu() on
hdev->conn_hash, as required by hci_conn_del().

hci_conn_put() is called outside hci_dev_unlock() so the final put
(which resolves to kfree() via bt_link_release) does not run under
hdev->lock, though the release path would be safe either way.

Without this, create_big_complete() would unconditionally
dereference the conn pointer on error, causing a use-after-free
via hci_connect_cfm() and hci_conn_del().

Fixes: eca0ae4aea66 ("Bluetooth: Add initial implementation of BIS connections")
Cc: stable@vger.kernel.org
Co-developed-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: David Carlier <devnexen@gmail.com>
---

v3 -> v4: combine v2's hci_dev_lock() wrapping in
  create_big_complete() with v3's refcount. hci_conn_del() now runs
  under hdev->lock as required by hci_conn_hash_del()'s
  list_del_rcu() on hdev->conn_hash (Pauli Virtanen review).
  hci_conn_put() is placed outside hci_dev_unlock() via a two-label
  unlock/done pattern so the final put (which resolves to kfree()
  via bt_link_release) does not nest under hdev->lock.
v2 -> v3 (Luiz): keep object alive across the async boundary via
  hci_conn_get() at the queue site and hci_conn_put() in the
  completion callback.
v1 -> v2: handle -ECANCELED and validate conn under hci_dev_lock()
  in create_big_complete().
v3: https://lore.kernel.org/r/20260410201343.229470-1-luiz.dentz@gmail.com
v1: https://lore.kernel.org/r/20260408155638.95927-1-devnexen@gmail.com
 net/bluetooth/hci_conn.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index 11d3ad8d2551..9fa6901aae9f 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -2130,6 +2130,9 @@ static int create_big_sync(struct hci_dev *hdev, void *data)
 	u32 flags = 0;
 	int err;
 
+	if (!hci_conn_valid(hdev, conn))
+		return -ECANCELED;
+
 	if (qos->bcast.out.phys == BIT(1))
 		flags |= MGMT_ADV_FLAG_SEC_2M;
 
@@ -2204,11 +2207,24 @@ static void create_big_complete(struct hci_dev *hdev, void *data, int err)
 
 	bt_dev_dbg(hdev, "conn %p", conn);
 
+	if (err == -ECANCELED)
+		goto done;
+
+	hci_dev_lock(hdev);
+
+	if (!hci_conn_valid(hdev, conn))
+		goto unlock;
+
 	if (err) {
 		bt_dev_err(hdev, "Unable to create BIG: %d", err);
 		hci_connect_cfm(conn, err);
 		hci_conn_del(conn);
 	}
+
+unlock:
+	hci_dev_unlock(hdev);
+done:
+	hci_conn_put(conn);
 }
 
 struct hci_conn *hci_bind_bis(struct hci_dev *hdev, bdaddr_t *dst, __u8 sid,
@@ -2336,10 +2352,11 @@ struct hci_conn *hci_connect_bis(struct hci_dev *hdev, bdaddr_t *dst,
 				 BT_BOUND, &data);
 
 	/* Queue start periodic advertising and create BIG */
-	err = hci_cmd_sync_queue(hdev, create_big_sync, conn,
+	err = hci_cmd_sync_queue(hdev, create_big_sync, hci_conn_get(conn),
 				 create_big_complete);
 	if (err < 0) {
 		hci_conn_drop(conn);
+		hci_conn_put(conn);
 		return ERR_PTR(err);
 	}
 
-- 
2.53.0

RE: [v4] Bluetooth: hci_conn: fix potential UAF in create_big_sync

[bluez.test.bot]

[-- Attachment #1: Type: text/plain, Size: 7138 bytes --]

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=1080419

---Test result---

Test Summary:
CheckPatch                    PENDING   0.32 seconds
GitLint                       PENDING   0.23 seconds
SubjectPrefix                 PASS      0.12 seconds
BuildKernel                   PASS      24.52 seconds
CheckAllWarning               PASS      26.88 seconds
CheckSparse                   PASS      26.00 seconds
BuildKernel32                 PASS      24.13 seconds
TestRunnerSetup               PASS      516.82 seconds
TestRunner_l2cap-tester       FAIL      27.49 seconds
TestRunner_iso-tester         PASS      43.05 seconds
TestRunner_bnep-tester        PASS      6.26 seconds
TestRunner_mgmt-tester        FAIL      110.72 seconds
TestRunner_rfcomm-tester      PASS      9.27 seconds
TestRunner_sco-tester         FAIL      14.14 seconds
TestRunner_ioctl-tester       PASS      10.11 seconds
TestRunner_mesh-tester        FAIL      12.48 seconds
TestRunner_smp-tester         PASS      8.53 seconds
TestRunner_userchan-tester    PASS      6.70 seconds
TestRunner_6lowpan-tester     FAIL      8.60 seconds
IncrementalBuild              PENDING   0.25 seconds

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

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

##############################
Test: TestRunner_l2cap-tester - FAIL
Desc: Run l2cap-tester with test-runner
Output:
Total: 96, Passed: 95 (99.0%), Failed: 1, Not Run: 0

Failed Test Cases
L2CAP BR/EDR Server - Set PHY 3M                     Failed       0.112 seconds
##############################
Test: TestRunner_mgmt-tester - FAIL
Desc: Run mgmt-tester with test-runner
Output:
Total: 494, Passed: 489 (99.0%), Failed: 1, Not Run: 4

Failed Test Cases
Read Exp Feature - Success                           Failed       0.103 seconds
##############################
Test: TestRunner_sco-tester - FAIL
Desc: Run sco-tester with test-runner
Output:
WARNING: possible circular locking dependency detected
7.0.0-rc2-gaf00b855bdd3 #1 Not tainted
------------------------------------------------------
kworker/u5:2/117 is trying to acquire lock:
ffff888001946240 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}, at: sco_connect_cfm+0x358/0x8d0

but task is already holding lock:
ffff888002141c20 (&conn->lock){+.+.}-{3:3}, at: sco_connect_cfm+0x22d/0x8d0

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&conn->lock){+.+.}-{3:3}:
       lock_acquire+0xf7/0x2c0
       _raw_spin_lock+0x2a/0x40
       sco_sock_connect+0x4d7/0x1280
       __sys_connect+0x1a3/0x260
       __x64_sys_connect+0x6e/0xb0
       do_syscall_64+0xa0/0x570
       entry_SYSCALL_64_after_hwframe+0x74/0x7c

-> #0 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}:
       check_prev_add+0xe9/0xc70
       __lock_acquire+0x1457/0x1df0
       lock_acquire+0xf7/0x2c0
       lock_sock_nested+0x36/0xd0
       sco_connect_cfm+0x358/0x8d0
       hci_sync_conn_complete_evt+0x3d3/0x8e0
       hci_event_packet+0x74f/0xb10
       hci_rx_work+0x398/0xd00
       process_scheduled_works+0xb16/0x1ac0
       worker_thread+0x4ff/0xba0
       kthread+0x368/0x490
       ret_from_fork+0x498/0x7e0
       ret_from_fork_asm+0x19/0x30

other info that might help us debug this:

...
BUG: sleeping function called from invalid context at net/core/sock.c:3782
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 117, name: kworker/u5:2
preempt_count: 1, expected: 0
RCU nest depth: 0, expected: 0
INFO: lockdep is turned off.
CPU: 0 UID: 0 PID: 117 Comm: kworker/u5:2 Not tainted 7.0.0-rc2-gaf00b855bdd3 #1 PREEMPT(lazy) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-1ubuntu1.1 04/01/2014
Workqueue: hci0 hci_rx_work
Call Trace:
 <TASK>
 dump_stack_lvl+0x49/0x60
 __might_resched+0x2ea/0x500
 lock_sock_nested+0x47/0xd0
 ? sco_connect_cfm+0x358/0x8d0
 sco_connect_cfm+0x358/0x8d0
 ? hci_debugfs_create_conn+0x190/0x210
 ? __pfx_sco_connect_cfm+0x10/0x10
 hci_sync_conn_complete_evt+0x3d3/0x8e0
 hci_event_packet+0x74f/0xb10
 ? __pfx_hci_sync_conn_complete_evt+0x10/0x10
 ? __pfx_hci_event_packet+0x10/0x10
 ? mark_held_locks+0x49/0x80
 ? lockdep_hardirqs_on_prepare+0xd4/0x180
 ? _raw_spin_unlock_irqrestore+0x2c/0x50
 hci_rx_work+0x398/0xd00
 process_scheduled_works+0xb16/0x1ac0
 ? __pfx_process_scheduled_works+0x10/0x10
 ? lock_acquire+0xf7/0x2c0
 ? lock_is_held_type+0x9b/0x110
 ? __pfx_hci_rx_work+0x10/0x10
 worker_thread+0x4ff/0xba0
 ? _raw_spin_unlock_irqrestore+0x2c/0x50
 ? __pfx_worker_thread+0x10/0x10
 kthread+0x368/0x490
 ? _raw_spin_unlock_irq+0x23/0x40
 ? __pfx_kthread+0x10/0x10
 ret_from_fork+0x498/0x7e0
 ? __pfx_ret_from_fork+0x10/0x10
 ? __switch_to+0x9e4/0xe50
 ? __switch_to_asm+0x32/0x60
...
Total: 30, Passed: 30 (100.0%), Failed: 0, Not Run: 0
##############################
Test: TestRunner_mesh-tester - FAIL
Desc: Run mesh-tester with test-runner
Output:
Total: 10, Passed: 8 (80.0%), Failed: 2, Not Run: 0

Failed Test Cases
Mesh - Send cancel - 1                               Timed out    2.699 seconds
Mesh - Send cancel - 2                               Timed out    1.995 seconds
##############################
Test: TestRunner_6lowpan-tester - FAIL
Desc: Run 6lowpan-tester with test-runner
Output:
WARNING: possible circular locking dependency detected
7.0.0-rc2-gaf00b855bdd3 #1 Not tainted
------------------------------------------------------
kworker/0:1/11 is trying to acquire lock:
ffff8880026e8940 ((wq_completion)hci0#2){+.+.}-{0:0}, at: touch_wq_lockdep_map+0x75/0x180

but task is already holding lock:
ffffffff8e64d720 (rtnl_mutex){+.+.}-{4:4}, at: lowpan_unregister_netdev+0xd/0x30

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 (rtnl_mutex){+.+.}-{4:4}:
       lock_acquire+0xf7/0x2c0
       __mutex_lock+0x16b/0x1fc0
       lowpan_register_netdev+0x11/0x30
       chan_ready_cb+0x836/0xd00
       l2cap_recv_frame+0x6a06/0x8920
       l2cap_recv_acldata+0x790/0xdf0
       hci_rx_work+0x500/0xd00
       process_scheduled_works+0xb16/0x1ac0
       worker_thread+0x4ff/0xba0
       kthread+0x368/0x490
       ret_from_fork+0x498/0x7e0
       ret_from_fork_asm+0x19/0x30

-> #3 (&chan->lock#3/1){+.+.}-{4:4}:
       lock_acquire+0xf7/0x2c0
       __mutex_lock+0x16b/0x1fc0
       l2cap_chan_connect+0x74e/0x1980
       lowpan_control_write+0x523/0x660
       full_proxy_write+0x10b/0x190
       vfs_write+0x1c0/0xf60
       ksys_write+0xf1/0x1d0
       do_syscall_64+0xa0/0x570
       entry_SYSCALL_64_after_hwframe+0x74/0x7c

-> #2 (&conn->lock){+.+.}-{4:4}:
...
Total: 8, Passed: 8 (100.0%), Failed: 0, Not Run: 0
##############################
Test: IncrementalBuild - PENDING
Desc: Incremental build with the patches in the series
Output:



https://github.com/bluez/bluetooth-next/pull/74

---
Regards,
Linux Bluetooth

Re: [PATCH v4] Bluetooth: hci_conn: fix potential UAF in create_big_sync

[patchwork-bot+bluetooth]

Hello:

This patch was applied to bluetooth/bluetooth-next.git (master)
by Luiz Augusto von Dentz <luiz.von.dentz@intel.com>:

On Sun, 12 Apr 2026 21:29:16 +0100 you wrote:
> Add hci_conn_valid() check in create_big_sync() to detect stale
> connections before proceeding with BIG creation. Handle the
> resulting -ECANCELED in create_big_complete() and re-validate the
> connection under hci_dev_lock() before dereferencing, matching the
> pattern used by create_le_conn_complete() and create_pa_complete().
> 
> Keep the hci_conn object alive across the async boundary by taking
> a reference via hci_conn_get() when queueing create_big_sync(), and
> dropping it in the completion callback. The refcount and the lock
> are complementary: the refcount keeps the object allocated, while
> hci_dev_lock() serializes hci_conn_hash_del()'s list_del_rcu() on
> hdev->conn_hash, as required by hci_conn_del().
> 
> [...]

Here is the summary with links:
  - [v4] Bluetooth: hci_conn: fix potential UAF in create_big_sync
    https://git.kernel.org/bluetooth/bluetooth-next/c/d55d107b6fa6

You are awesome, thank you!
-- 
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