[PATCH] Bluetooth: SCO: fix sleeping under spinlock in sco_conn_ready

[PATCH] Bluetooth: SCO: fix sleeping under spinlock in sco_conn_ready

[Pauli Virtanen]

sco_conn_ready calls sleeping functions under conn->lock spinlock.

The critical section can be reduced: conn->hcon is modified only with
hdev->lock held. It is guaranteed to be held in sco_conn_ready, so
conn->lock is not needed to guard it.

Move taking conn->lock after lock_sock(parent). This also follows the
lock ordering lock_sock() > conn->lock elsewhere in the file.

Fixes: 27c24fda62b60 ("Bluetooth: switch to lock_sock in SCO")
Signed-off-by: Pauli Virtanen <pav@iki.fi>
---
 net/bluetooth/sco.c | 20 +++++++++-----------
 1 file changed, 9 insertions(+), 11 deletions(-)

diff --git a/net/bluetooth/sco.c b/net/bluetooth/sco.c
index 18826d4b9c0b..3a5479538e85 100644
--- a/net/bluetooth/sco.c
+++ b/net/bluetooth/sco.c
@@ -1377,26 +1377,24 @@ static void sco_conn_ready(struct sco_conn *conn)
 		sk->sk_state_change(sk);
 		release_sock(sk);
 	} else {
-		sco_conn_lock(conn);
-
-		if (!conn->hcon) {
-			sco_conn_unlock(conn);
+		if (!conn->hcon)
 			return;
-		}
+
+		lockdep_assert_held(&conn->hcon->hdev->lock);
 
 		parent = sco_get_sock_listen(&conn->hcon->src);
-		if (!parent) {
-			sco_conn_unlock(conn);
+		if (!parent)
 			return;
-		}
 
 		lock_sock(parent);
 
+		sco_conn_lock(conn);
+
 		sk = sco_sock_alloc(sock_net(parent), NULL,
 				    BTPROTO_SCO, GFP_ATOMIC, 0);
 		if (!sk) {
-			release_sock(parent);
 			sco_conn_unlock(conn);
+			release_sock(parent);
 			return;
 		}
 
@@ -1417,9 +1415,9 @@ static void sco_conn_ready(struct sco_conn *conn)
 		/* Wake up parent */
 		parent->sk_data_ready(parent);
 
-		release_sock(parent);
-
 		sco_conn_unlock(conn);
+
+		release_sock(parent);
 	}
 }
 
-- 
2.53.0

RE: Bluetooth: SCO: fix sleeping under spinlock in sco_conn_ready

[bluez.test.bot]

[-- Attachment #1: Type: text/plain, Size: 4177 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=1080410

---Test result---

Test Summary:
CheckPatch                    PENDING   0.50 seconds
GitLint                       PENDING   0.30 seconds
SubjectPrefix                 PASS      0.08 seconds
BuildKernel                   PASS      23.67 seconds
CheckAllWarning               PASS      26.30 seconds
CheckSparse                   PASS      24.97 seconds
BuildKernel32                 PASS      23.06 seconds
TestRunnerSetup               PASS      517.43 seconds
TestRunner_l2cap-tester       FAIL      27.72 seconds
TestRunner_iso-tester         PASS      32.92 seconds
TestRunner_bnep-tester        PASS      6.26 seconds
TestRunner_mgmt-tester        FAIL      110.65 seconds
TestRunner_rfcomm-tester      PASS      9.28 seconds
TestRunner_sco-tester         PASS      14.05 seconds
TestRunner_ioctl-tester       PASS      9.98 seconds
TestRunner_mesh-tester        FAIL      11.46 seconds
TestRunner_smp-tester         PASS      8.44 seconds
TestRunner_userchan-tester    PASS      6.50 seconds
TestRunner_6lowpan-tester     FAIL      8.83 seconds
IncrementalBuild              PENDING   0.30 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 2M                     Failed       0.114 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       0.102 seconds
##############################
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    1.829 seconds
Mesh - Send cancel - 2                               Timed out    2.004 seconds
##############################
Test: TestRunner_6lowpan-tester - FAIL
Desc: Run 6lowpan-tester with test-runner
Output:
WARNING: possible circular locking dependency detected
7.0.0-rc2-g48abf361eec2 #1 Not tainted
------------------------------------------------------
kworker/0:1/11 is trying to acquire lock:
ffff888002767140 ((wq_completion)hci0#2){+.+.}-{0:0}, at: touch_wq_lockdep_map+0x75/0x180

but task is already holding lock:
ffffffff8844d720 (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/72

---
Regards,
Linux Bluetooth

Re: [PATCH] Bluetooth: SCO: fix sleeping under spinlock in sco_conn_ready

[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 21:47:42 +0300 you wrote:
> sco_conn_ready calls sleeping functions under conn->lock spinlock.
> 
> The critical section can be reduced: conn->hcon is modified only with
> hdev->lock held. It is guaranteed to be held in sco_conn_ready, so
> conn->lock is not needed to guard it.
> 
> Move taking conn->lock after lock_sock(parent). This also follows the
> lock ordering lock_sock() > conn->lock elsewhere in the file.
> 
> [...]

Here is the summary with links:
  - Bluetooth: SCO: fix sleeping under spinlock in sco_conn_ready
    https://git.kernel.org/bluetooth/bluetooth-next/c/d87bd74aeb54

You are awesome, thank you!
-- 
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