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Bluetooth: hci_conn: fix potential UAF in create_big_sync

PATCH In review Luiz Augusto von Dentz 4 participants 4 messages Apr 10 – Apr 11

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Luiz Augusto von Dentz

author maintainer
#0 lore raw

PATCH v3 1/1 Bluetooth: hci_conn: fix potential UAF in create_big_sync

From: David Carlier <[email protected]>

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

Without this, create_big_complete() would unconditionally dereference the stale 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 [email protected]
Signed-off-by David Carlier <[email protected]>
Signed-off-by Luiz Augusto von Dentz <[email protected]>
---
 net/bluetooth/hci_conn.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)
net/bluetooth/hci_conn.c +11 -1
index 3a0592599086..7e6b3542809c 100644
@@ -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 +2207,17 @@ 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;
+
 	if (err) {
 		bt_dev_err(hdev, "Unable to create BIG: %d", err);
 		hci_connect_cfm(conn, err);
 		hci_conn_del(conn);
 	}
+
+done:
+	hci_conn_put(conn);
 }
 
 struct hci_conn *hci_bind_bis(struct hci_dev *hdev, bdaddr_t *dst, __u8 sid,

@@ -2336,10 +2345,11 @@ 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);
 	}
Signature · 1 line
2.53.0
#1 lore raw

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=1079916

---Test result---

Test Summary:

CheckPatch                    PENDING   0.41 seconds
GitLint                       PENDING   0.29 seconds
SubjectPrefix                 PASS      0.13 seconds
BuildKernel                   PASS      26.17 seconds
CheckAllWarning               PASS      28.87 seconds
CheckSparse                   PASS      27.44 seconds
BuildKernel32                 PASS      25.68 seconds
TestRunnerSetup               PASS      568.50 seconds
TestRunner_l2cap-tester       PASS      28.60 seconds
TestRunner_iso-tester         PASS      38.29 seconds
TestRunner_bnep-tester        PASS      6.45 seconds
TestRunner_mgmt-tester        FAIL      114.64 seconds
TestRunner_rfcomm-tester      PASS      9.50 seconds
TestRunner_sco-tester         FAIL      14.45 seconds
TestRunner_ioctl-tester       PASS      10.41 seconds
TestRunner_mesh-tester        FAIL      12.49 seconds
TestRunner_smp-tester         PASS      10.61 seconds
TestRunner_userchan-tester    PASS      6.80 seconds
TestRunner_6lowpan-tester     FAIL      8.77 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_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 0.109 seconds
##############################
Test: TestRunner_sco-tester - FAIL
Desc: Run sco-tester with test-runner
Output:
WARNING: possible circular locking dependency detected
7.0.0-rc2-g9147c3c53c80 #1 Not tainted
------------------------------------------------------
kworker/u5:2/117 is trying to acquire lock:
ffff888001c66240 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}, at: sco_connect_cfm+0x358/0x8d0

but task is already holding lock:
ffff888002607220 (&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-g9147c3c53c80 #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    2.600 seconds
Mesh - Send cancel - 2                               Timed out    1.996 seconds

##############################
Test: TestRunner_6lowpan-tester - FAIL
Desc: Run 6lowpan-tester with test-runner
Output:
WARNING: possible circular locking dependency detected 7.0.0-rc2-g9147c3c53c80 #1 Not tainted
------------------------------------------------------
kworker/0:1/11 is trying to acquire lock:
ffff8880026e0940 ((wq_completion)hci0#2){+.+.}-{0:0}, at: touch_wq_lockdep_map+0x75/0x180

but task is already holding lock:
ffffffff9064d720 (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/66

---
Regards,
Linux Bluetooth

#2 lore raw
In reply to Luiz Augusto von Dentz

Hi,

pe, 2026-04-10 kello 16:13 -0400, Luiz Augusto von Dentz kirjoitti:

Quoted 36 lines

From: David Carlier <[email protected]>

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

Without this, create_big_complete() would unconditionally dereference the stale 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 [email protected]
Signed-off-by David Carlier <[email protected]>
Signed-off-by Luiz Augusto von Dentz <[email protected]>
---
 net/bluetooth/hci_conn.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)
net/bluetooth/hci_conn.c +3 -0
index 3a0592599086..7e6b3542809c 100644
@@ -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;

net/bluetooth/hci_conn.c static void create_big_complete(struct hci_dev *hdev, void *data, int err) · line 2216

Quoted 10 lines
net/bluetooth/hci_conn.c +3 -0
@@ -2204,11 +2207,17 @@ 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;
+
 	if (err) {
 		bt_dev_err(hdev, "Unable to create BIG: %d", err);
 		hci_connect_cfm(conn, err);
 		hci_conn_del(conn);

hci_conn_del() is called without hci_dev_lock() here.

It probably should take the lock and check hci_conn_valid() inside the critical section before calling into hci_conn_del().

Probably hci_conn_del() should have lockdep_assert_held(&hdev->lock)

Quoted 20 lines
net/bluetooth/hci_conn.c +5 -1
 	}
+
+done:
+	hci_conn_put(conn);
 }
 
 struct hci_conn *hci_bind_bis(struct hci_dev *hdev, bdaddr_t *dst, __u8 sid,

@@ -2336,10 +2345,11 @@ 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);
 	}
Signature · 1 line
Pauli Virtanen
#3 lore raw

Hi Pauli,

Good catch. I think you're right — hci_conn_del() ends up in
hci_conn_hash_del() which does list_del_rcu() + synchronize_rcu() on hdev->conn_hash, so the call really
does want hdev->lock held around it, not just a refcount keeping the
object allocated.

Wrapping the hci_connect_cfm() / hci_conn_del() pair in
hci_dev_lock() and re-checking hci_conn_valid() inside the critical section would also bring
create_big_complete() in line with what create_le_conn_complete()
and create_pa_complete() already do, which is nice for consistency.

The lockdep_assert_held(&hdev->lock) in hci_conn_del() sounds
reasonable as a follow-up — it'd catch exactly this kind of thing. I can take a look at whether all
existing call sites already satisfy it before proposing it separately.

Luiz, let me know if you'd like me to respin, or whether you prefer
to fold it into a v4 yourself.

Cheers !

Quoted 81 lines · Pauli Virtanen

Hi,

pe, 2026-04-10 kello 16:13 -0400, Luiz Augusto von Dentz kirjoitti:

Quoted 36 lines

From: David Carlier <[email protected]>

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

Without this, create_big_complete() would unconditionally dereference the stale 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 [email protected]
Signed-off-by David Carlier <[email protected]>
Signed-off-by Luiz Augusto von Dentz <[email protected]>
---
 net/bluetooth/hci_conn.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)
net/bluetooth/hci_conn.c +3 -0
index 3a0592599086..7e6b3542809c 100644
@@ -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;

net/bluetooth/hci_conn.c static void create_big_complete(struct hci_dev *hdev, void *data, int err) · line 2216

Quoted 10 lines
net/bluetooth/hci_conn.c +3 -0
@@ -2204,11 +2207,17 @@ 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;
+
      if (err) {
              bt_dev_err(hdev, "Unable to create BIG: %d", err);
              hci_connect_cfm(conn, err);
              hci_conn_del(conn);

hci_conn_del() is called without hci_dev_lock() here.

It probably should take the lock and check hci_conn_valid() inside the critical section before calling into hci_conn_del().

Probably hci_conn_del() should have lockdep_assert_held(&hdev->lock)

Quoted 10 lines
net/bluetooth/hci_conn.c +3 -0
      }
+
+done:
+     hci_conn_put(conn);
 }
 
 struct hci_conn *hci_bind_bis(struct hci_dev *hdev, bdaddr_t *dst, __u8 sid,

@@ -2336,10 +2345,11 @@ struct hci_conn *hci_connect_bis(struct hci_dev *hdev, bdaddr_t *dst,
                               BT_BOUND, &data);

net/bluetooth/hci_conn.c struct hci_conn *hci_connect_bis(struct hci_dev *hdev, bdaddr_t *dst, · line 2355

Quoted 10 lines
net/bluetooth/hci_conn.c +2 -1
      /* 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);
      }

--
Pauli Virtanen