[v3,1/2] Bluetooth: ISO: Fix circular locking dependency warning

Commit Message

Iulia Tanasescu March 7, 2024, 1:58 p.m. UTC

This fixes the circular locking dependency warning caused
by iso_listen_bis acquiring the hdev lock while the socket
has been locked in the caller function.

======================================================
WARNING: possible circular locking dependency detected
6.8.0-rc5+ #1 Not tainted
------------------------------------------------------
iso-tester/2950 is trying to acquire lock:
ffff88817a048080 (&hdev->lock){+.+.}-{3:3}, at: iso_sock_listen+0x305/0x8d0

               but task is already holding lock:
ffff888197c39278 (sk_lock-AF_BLUETOOTH-BTPROTO_ISO){+.+.}-{0:0},
               at: iso_sock_listen+0x91/0x8d0

               which lock already depends on the new lock.

               the existing dependency chain (in reverse order) is:

 -> #1 (sk_lock-AF_BLUETOOTH-BTPROTO_ISO){+.+.}-{0:0}:
        lock_sock_nested+0x3b/0xb0
        iso_connect_cis+0x185/0x540
        iso_sock_connect+0x445/0x7e0
        __sys_connect_file+0xd5/0x100
        __sys_connect+0x11e/0x150
        __x64_sys_connect+0x42/0x60
        do_syscall_64+0x8d/0x150
        entry_SYSCALL_64_after_hwframe+0x6e/0x76

-> #0 (&hdev->lock){+.+.}-{3:3}:
        __lock_acquire+0x208f/0x3720
        lock_acquire+0x16d/0x3f0
        __mutex_lock+0x155/0x1310
        mutex_lock_nested+0x1b/0x30
        iso_sock_listen+0x305/0x8d0
        __sys_listen+0x106/0x190
        __x64_sys_listen+0x30/0x40
        do_syscall_64+0x8d/0x150
        entry_SYSCALL_64_after_hwframe+0x6e/0x76

        other info that might help us debug this:

Possible unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   lock(sk_lock-AF_BLUETOOTH-BTPROTO_ISO);
                                lock(&hdev->lock);
                                lock(sk_lock-AF_BLUETOOTH-BTPROTO_ISO);
   lock(&hdev->lock);

                *** DEADLOCK ***

1 lock held by iso-tester/2950:
0: ffff888197c39278 (sk_lock-AF_BLUETOOTH-BTPROTO_ISO){+.+.}-{0:0},
                at: iso_sock_listen+0x91/0x8d0

Signed-off-by: Iulia Tanasescu <[e-mail]>
---
 net/bluetooth/iso.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

Comments

[e-mail] March 7, 2024, 2:32 p.m. UTC | #1

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=833415

---Test result---

Test Summary:
CheckPatch                    PASS      1.37 seconds
GitLint                       PASS      0.68 seconds
SubjectPrefix                 PASS      0.27 seconds
BuildKernel                   PASS      27.93 seconds
CheckAllWarning               PASS      30.81 seconds
CheckSparse                   PASS      36.29 seconds
CheckSmatch                   PASS      99.01 seconds
BuildKernel32                 PASS      27.04 seconds
TestRunnerSetup               PASS      499.86 seconds
TestRunner_l2cap-tester       PASS      19.96 seconds
TestRunner_iso-tester         PASS      31.12 seconds
TestRunner_bnep-tester        PASS      4.74 seconds
TestRunner_mgmt-tester        PASS      109.98 seconds
TestRunner_rfcomm-tester      PASS      7.30 seconds
TestRunner_sco-tester         PASS      14.90 seconds
TestRunner_ioctl-tester       PASS      7.80 seconds
TestRunner_mesh-tester        PASS      5.93 seconds
TestRunner_smp-tester         PASS      6.82 seconds
TestRunner_userchan-tester    PASS      4.91 seconds
IncrementalBuild              PASS      30.87 seconds



---
Regards,
Linux Bluetooth

Patch

diff --git a/net/bluetooth/iso.c b/net/bluetooth/iso.c
index 8af75d37b14c..d1608387fd85 100644
--- a/net/bluetooth/iso.c
+++ b/net/bluetooth/iso.c
@@ -1069,6 +1069,7 @@  static int iso_sock_connect(struct socket *sock, struct sockaddr *addr,
 	return err;
 }
 
+/* This function requires the caller to hold sk lock */
 static int iso_listen_bis(struct sock *sk)
 {
 	struct hci_dev *hdev;
@@ -1095,7 +1096,15 @@  static int iso_listen_bis(struct sock *sk)
 	if (!hdev)
 		return -EHOSTUNREACH;
 
+	/* Prevent sk from being freed whilst unlocked */
+	sock_hold(sk);
+
+	/* To avoid circular locking dependencies,
+	 * hdev should be locked first before sk.
+	 */
+	release_sock(sk);
 	hci_dev_lock(hdev);
+	lock_sock(sk);
 
 	/* Fail if user set invalid QoS */
 	if (iso_pi(sk)->qos_user_set && !check_bcast_qos(&iso_pi(sk)->qos)) {
@@ -1128,7 +1137,13 @@  static int iso_listen_bis(struct sock *sk)
 	hci_dev_put(hdev);
 
 unlock:
+	/* Unlock order should be in reverse from lock order. */
+	release_sock(sk);
 	hci_dev_unlock(hdev);
+	lock_sock(sk);
+
+	sock_put(sk);
+
 	return err;
 }