[PATCH v2] Bluetooth: L2CAP: Fix deadlock in l2cap_conn_del()

[PATCH v2] Bluetooth: L2CAP: Fix deadlock in l2cap_conn_del()

[Hyunwoo Kim]

l2cap_conn_del() calls cancel_delayed_work_sync() for both info_timer
and id_addr_timer while holding conn->lock. However, the work functions
l2cap_info_timeout() and l2cap_conn_update_id_addr() both acquire
conn->lock, creating a potential AB-BA deadlock if the work is already
executing when l2cap_conn_del() takes the lock.

Move the work cancellations before acquiring conn->lock and use
disable_delayed_work_sync() to additionally prevent the works from
being rearmed after cancellation, consistent with the pattern used in
hci_conn_del().

Fixes: ab4eedb790ca ("Bluetooth: L2CAP: Fix corrupted list in hci_chan_del")
Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
---
Changes in v2:
- Replace cancel_delayed_work_sync() with disable_delayed_work_sync()
- v1: https://lore.kernel.org/all/abwTQVhyDv0_x26G@v4bel/
---
 net/bluetooth/l2cap_core.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 5deb6c4f1e41..b279620ed209 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -1748,6 +1748,9 @@ static void l2cap_conn_del(struct hci_conn *hcon, int err)
 
 	BT_DBG("hcon %p conn %p, err %d", hcon, conn, err);
 
+	disable_delayed_work_sync(&conn->info_timer);
+	disable_delayed_work_sync(&conn->id_addr_timer);
+
 	mutex_lock(&conn->lock);
 
 	kfree_skb(conn->rx_skb);
@@ -1763,8 +1766,6 @@ static void l2cap_conn_del(struct hci_conn *hcon, int err)
 
 	ida_destroy(&conn->tx_ida);
 
-	cancel_delayed_work_sync(&conn->id_addr_timer);
-
 	l2cap_unregister_all_users(conn);
 
 	/* Force the connection to be immediately dropped */
@@ -1783,9 +1784,6 @@ static void l2cap_conn_del(struct hci_conn *hcon, int err)
 		l2cap_chan_put(chan);
 	}
 
-	if (conn->info_state & L2CAP_INFO_FEAT_MASK_REQ_SENT)
-		cancel_delayed_work_sync(&conn->info_timer);
-
 	hci_chan_del(conn->hchan);
 	conn->hchan = NULL;
 
-- 
2.43.0

RE: [v2] Bluetooth: L2CAP: Fix deadlock in l2cap_conn_del()

[bluez.test.bot]

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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=1069844

---Test result---

Test Summary:
CheckPatch                    PENDING   0.36 seconds
GitLint                       PENDING   0.29 seconds
SubjectPrefix                 PASS      0.12 seconds
BuildKernel                   PASS      26.71 seconds
CheckAllWarning               PASS      29.15 seconds
CheckSparse                   PASS      28.09 seconds
BuildKernel32                 PASS      25.78 seconds
TestRunnerSetup               PASS      573.72 seconds
TestRunner_l2cap-tester       PASS      27.99 seconds
TestRunner_iso-tester         FAIL      36.79 seconds
TestRunner_bnep-tester        PASS      6.48 seconds
TestRunner_mgmt-tester        FAIL      115.17 seconds
TestRunner_rfcomm-tester      PASS      9.64 seconds
TestRunner_sco-tester         FAIL      14.54 seconds
TestRunner_ioctl-tester       PASS      10.48 seconds
TestRunner_mesh-tester        FAIL      12.65 seconds
TestRunner_smp-tester         PASS      8.74 seconds
TestRunner_userchan-tester    PASS      6.88 seconds
IncrementalBuild              PENDING   0.46 seconds

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

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

##############################
Test: TestRunner_iso-tester - FAIL
Desc: Run iso-tester with test-runner
Output:
BUG: KASAN: slab-use-after-free in le_read_features_complete+0x7e/0x2b0
Total: 141, Passed: 141 (100.0%), Failed: 0, Not Run: 0
##############################
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
BUG: sleeping function called from invalid context at net/core/sock.c:3782
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    2.758 seconds
Mesh - Send cancel - 2                               Timed out    1.994 seconds
##############################
Test: IncrementalBuild - PENDING
Desc: Incremental build with the patches in the series
Output:



---
Regards,
Linux Bluetooth

Re: [PATCH v2] Bluetooth: L2CAP: Fix deadlock in l2cap_conn_del()

[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 Fri, 20 Mar 2026 20:01:26 +0900 you wrote:
> l2cap_conn_del() calls cancel_delayed_work_sync() for both info_timer
> and id_addr_timer while holding conn->lock. However, the work functions
> l2cap_info_timeout() and l2cap_conn_update_id_addr() both acquire
> conn->lock, creating a potential AB-BA deadlock if the work is already
> executing when l2cap_conn_del() takes the lock.
> 
> Move the work cancellations before acquiring conn->lock and use
> disable_delayed_work_sync() to additionally prevent the works from
> being rearmed after cancellation, consistent with the pattern used in
> hci_conn_del().
> 
> [...]

Here is the summary with links:
  - [v2] Bluetooth: L2CAP: Fix deadlock in l2cap_conn_del()
    https://git.kernel.org/bluetooth/bluetooth-next/c/f6bba07f059c

You are awesome, thank you!
-- 
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