Bluetooth: hci_conn: fix potential UAF in create_big_sync
Subsystems (3)
PATCH v4 1/1 Bluetooth: hci_conn: fix potential UAF in create_big_sync
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().
---
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/[email protected]
v1: https://lore.kernel.org/r/[email protected]
net/bluetooth/hci_conn.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-)
net/bluetooth/hci_conn.c +18 -1
@@ -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); }
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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=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+0x19/0x30other 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/u5:2preempt_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
This patch was applied to bluetooth/bluetooth-next.git (master) by Luiz Augusto von Dentz <[email protected]>:
Hello:
This patch was applied to bluetooth/bluetooth-next.git (master) by Luiz Augusto von Dentz <[email protected]>:
Quoted 6 lines · On Sun, 12 Apr 2026 21:29:16 +0100 you wrote:
Add
hci_conn_valid()check increate_big_sync()to detect stale connections before proceeding with BIG creation. Handle the resulting-ECANCELEDincreate_big_complete()and re-validate the connection underhci_dev_lock()before dereferencing, matching the pattern used bycreate_le_conn_complete()andcreate_pa_complete().
Quoted 8 lines
Keep the
hci_connobject alive across the async boundary by taking a reference viahci_conn_get()when queueingcreate_big_sync(), and dropping it in the completion callback. The refcount and the lock are complementary: the refcount keeps the object allocated, whilehci_dev_lock()serializes hci_conn_hash_del()'slist_del_rcu()onhdev->conn_hash, as required byhci_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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