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Below is an example of a warning generated because of locking dependencies: [ 75.307983] ====================================================== [ 75.307984] WARNING: possible circular locking dependency detected [ 75.307985] 6.12.0-rc6+ #22 Not tainted [ 75.307987] ------------------------------------------------------ [ 75.307987] kworker/u81:2/2623 is trying to acquire lock: [ 75.307988] ffff8fde1769da58 (sk_lock-AF_BLUETOOTH-BTPROTO_ISO) at: iso_connect_cfm+0x253/0x840 [bluetooth] [ 75.308021] but task is already holding lock: [ 75.308022] ffff8fdd61a10078 (&hdev->lock) at: hci_le_per_adv_report_evt+0x47/0x2f0 [bluetooth] [ 75.308053] which lock already depends on the new lock. [ 75.308054] the existing dependency chain (in reverse order) is: [ 75.308055] -> #1 (&hdev->lock){+.+.}-{3:3}: [ 75.308057] __mutex_lock+0xad/0xc50 [ 75.308061] mutex_lock_nested+0x1b/0x30 [ 75.308063] iso_sock_listen+0x143/0x5c0 [bluetooth] [ 75.308085] __sys_listen_socket+0x49/0x60 [ 75.308088] __x64_sys_listen+0x4c/0x90 [ 75.308090] x64_sys_call+0x2517/0x25f0 [ 75.308092] do_syscall_64+0x87/0x150 [ 75.308095] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 75.308098] -> #0 (sk_lock-AF_BLUETOOTH-BTPROTO_ISO){+.+.}-{0:0}: [ 75.308100] __lock_acquire+0x155e/0x25f0 [ 75.308103] lock_acquire+0xc9/0x300 [ 75.308105] lock_sock_nested+0x32/0x90 [ 75.308107] iso_connect_cfm+0x253/0x840 [bluetooth] [ 75.308128] hci_connect_cfm+0x6c/0x190 [bluetooth] [ 75.308155] hci_le_per_adv_report_evt+0x27b/0x2f0 [bluetooth] [ 75.308180] hci_le_meta_evt+0xe7/0x200 [bluetooth] [ 75.308206] hci_event_packet+0x21f/0x5c0 [bluetooth] [ 75.308230] hci_rx_work+0x3ae/0xb10 [bluetooth] [ 75.308254] process_one_work+0x212/0x740 [ 75.308256] worker_thread+0x1bd/0x3a0 [ 75.308258] kthread+0xe4/0x120 [ 75.308259] ret_from_fork+0x44/0x70 [ 75.308261] ret_from_fork_asm+0x1a/0x30 [ 75.308263] other info that might help us debug this: [ 75.308264] Possible unsafe locking scenario: [ 75.308264] CPU0 CPU1 [ 75.308265] ---- ---- [ 75.308265] lock(&hdev->lock); [ 75.308267] lock(sk_lock- AF_BLUETOOTH-BTPROTO_ISO); [ 75.308268] lock(&hdev->lock); [ 75.308269] lock(sk_lock-AF_BLUETOOTH-BTPROTO_ISO); [ 75.308270] *** DEADLOCK *** [ 75.308271] 4 locks held by kworker/u81:2/2623: [ 75.308272] #0: ffff8fdd66e52148 ((wq_completion)hci0#2){+.+.}-{0:0}, at: process_one_work+0x443/0x740 [ 75.308276] #1: ffffafb488b7fe48 ((work_completion)(&hdev->rx_work)), at: process_one_work+0x1ce/0x740 [ 75.308280] #2: ffff8fdd61a10078 (&hdev->lock){+.+.}-{3:3} at: hci_le_per_adv_report_evt+0x47/0x2f0 [bluetooth] [ 75.308304] #3: ffffffffb6ba4900 (rcu_read_lock){....}-{1:2}, at: hci_connect_cfm+0x29/0x190 [bluetooth] Signed-off-by: Iulia Tanasescu --- net/bluetooth/iso.c | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) diff --git a/net/bluetooth/iso.c b/net/bluetooth/iso.c index 8ed818254dc8..cb004b678d65 100644 --- a/net/bluetooth/iso.c +++ b/net/bluetooth/iso.c @@ -1102,6 +1102,7 @@ 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; @@ -1128,7 +1129,15 @@ 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)) { @@ -1161,7 +1170,13 @@ 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; } @@ -1417,6 +1432,7 @@ static void iso_conn_defer_accept(struct hci_conn *conn) hci_send_cmd(hdev, HCI_OP_LE_ACCEPT_CIS, sizeof(cp), &cp); } +/* This function requires the caller to hold sk lock */ static void iso_conn_big_sync(struct sock *sk) { int err; @@ -1428,6 +1444,14 @@ static void iso_conn_big_sync(struct sock *sk) if (!hdev) return; + /* 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_le_big_create_sync requires hdev lock to be held, since * it enqueues the HCI LE BIG Create Sync command via * hci_cmd_sync_queue_once, which checks hdev flags that might @@ -1435,6 +1459,8 @@ static void iso_conn_big_sync(struct sock *sk) */ hci_dev_lock(hdev); + lock_sock(sk); + if (!test_and_set_bit(BT_SK_BIG_SYNC, &iso_pi(sk)->flags)) { err = hci_le_big_create_sync(hdev, iso_pi(sk)->conn->hcon, &iso_pi(sk)->qos, @@ -1446,7 +1472,12 @@ static void iso_conn_big_sync(struct sock *sk) err); } + /* Unlock order should be in reverse from lock order. */ + release_sock(sk); hci_dev_unlock(hdev); + lock_sock(sk); + + sock_put(sk); } static int iso_sock_recvmsg(struct socket *sock, struct msghdr *msg,