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Mon, 09 Aug 2021 21:17:14 -0700 (PDT) From: Desmond Cheong Zhi Xi To: marcel@holtmann.org, johan.hedberg@gmail.com, luiz.dentz@gmail.com, davem@davemloft.net, kuba@kernel.org, sudipm.mukherjee@gmail.com Subject: [PATCH v6 2/6] Bluetooth: avoid circular locks in sco_sock_connect Date: Tue, 10 Aug 2021 12:14:06 +0800 Message-Id: <20210810041410.142035-3-desmondcheongzx@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210810041410.142035-1-desmondcheongzx@gmail.com> References: <20210810041410.142035-1-desmondcheongzx@gmail.com> MIME-Version: 1.0 Cc: linux-kernel@vger.kernel.org, linux-bluetooth@vger.kernel.org, netdev@vger.kernel.org, Desmond Cheong Zhi Xi , linux-kernel-mentees@lists.linuxfoundation.org X-BeenThere: linux-kernel-mentees@lists.linuxfoundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-kernel-mentees-bounces@lists.linuxfoundation.org Sender: "Linux-kernel-mentees" In a future patch, calls to bh_lock_sock in sco.c should be replaced by lock_sock now that none of the functions are run in IRQ context. However, doing so results in a circular locking dependency: ====================================================== WARNING: possible circular locking dependency detected 5.14.0-rc4-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.2/14867 is trying to acquire lock: ffff88803e3c1120 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1613 [inline] ffff88803e3c1120 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}, at: sco_conn_del+0x12a/0x2a0 net/bluetooth/sco.c:191 but task is already holding lock: ffffffff8d2dc7c8 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_disconn_cfm include/net/bluetooth/hci_core.h:1497 [inline] ffffffff8d2dc7c8 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_conn_hash_flush+0xda/0x260 net/bluetooth/hci_conn.c:1608 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (hci_cb_list_lock){+.+.}-{3:3}: __mutex_lock_common kernel/locking/mutex.c:959 [inline] __mutex_lock+0x12a/0x10a0 kernel/locking/mutex.c:1104 hci_connect_cfm include/net/bluetooth/hci_core.h:1482 [inline] hci_remote_features_evt net/bluetooth/hci_event.c:3263 [inline] hci_event_packet+0x2f4d/0x7c50 net/bluetooth/hci_event.c:6240 hci_rx_work+0x4f8/0xd30 net/bluetooth/hci_core.c:5122 process_one_work+0x98d/0x1630 kernel/workqueue.c:2276 worker_thread+0x658/0x11f0 kernel/workqueue.c:2422 kthread+0x3e5/0x4d0 kernel/kthread.c:319 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 -> #1 (&hdev->lock){+.+.}-{3:3}: __mutex_lock_common kernel/locking/mutex.c:959 [inline] __mutex_lock+0x12a/0x10a0 kernel/locking/mutex.c:1104 sco_connect net/bluetooth/sco.c:245 [inline] sco_sock_connect+0x227/0xa10 net/bluetooth/sco.c:601 __sys_connect_file+0x155/0x1a0 net/socket.c:1879 __sys_connect+0x161/0x190 net/socket.c:1896 __do_sys_connect net/socket.c:1906 [inline] __se_sys_connect net/socket.c:1903 [inline] __x64_sys_connect+0x6f/0xb0 net/socket.c:1903 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae -> #0 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}: check_prev_add kernel/locking/lockdep.c:3051 [inline] check_prevs_add kernel/locking/lockdep.c:3174 [inline] validate_chain kernel/locking/lockdep.c:3789 [inline] __lock_acquire+0x2a07/0x54a0 kernel/locking/lockdep.c:5015 lock_acquire kernel/locking/lockdep.c:5625 [inline] lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5590 lock_sock_nested+0xca/0x120 net/core/sock.c:3170 lock_sock include/net/sock.h:1613 [inline] sco_conn_del+0x12a/0x2a0 net/bluetooth/sco.c:191 sco_disconn_cfm+0x71/0xb0 net/bluetooth/sco.c:1202 hci_disconn_cfm include/net/bluetooth/hci_core.h:1500 [inline] hci_conn_hash_flush+0x127/0x260 net/bluetooth/hci_conn.c:1608 hci_dev_do_close+0x528/0x1130 net/bluetooth/hci_core.c:1778 hci_unregister_dev+0x1c0/0x5a0 net/bluetooth/hci_core.c:4015 vhci_release+0x70/0xe0 drivers/bluetooth/hci_vhci.c:340 __fput+0x288/0x920 fs/file_table.c:280 task_work_run+0xdd/0x1a0 kernel/task_work.c:164 exit_task_work include/linux/task_work.h:32 [inline] do_exit+0xbd4/0x2a60 kernel/exit.c:825 do_group_exit+0x125/0x310 kernel/exit.c:922 get_signal+0x47f/0x2160 kernel/signal.c:2808 arch_do_signal_or_restart+0x2a9/0x1c40 arch/x86/kernel/signal.c:865 handle_signal_work kernel/entry/common.c:148 [inline] exit_to_user_mode_loop kernel/entry/common.c:172 [inline] exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:209 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline] syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:302 ret_from_fork+0x15/0x30 arch/x86/entry/entry_64.S:288 other info that might help us debug this: Chain exists of: sk_lock-AF_BLUETOOTH-BTPROTO_SCO --> &hdev->lock --> hci_cb_list_lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(hci_cb_list_lock); lock(&hdev->lock); lock(hci_cb_list_lock); lock(sk_lock-AF_BLUETOOTH-BTPROTO_SCO); *** DEADLOCK *** The issue is that the lock hierarchy should go from &hdev->lock --> hci_cb_list_lock --> sk_lock-AF_BLUETOOTH-BTPROTO_SCO. For example, one such call trace is: hci_dev_do_close(): hci_dev_lock(); hci_conn_hash_flush(): hci_disconn_cfm(): mutex_lock(&hci_cb_list_lock); sco_disconn_cfm(): sco_conn_del(): lock_sock(sk); However, in sco_sock_connect, we call lock_sock before calling hci_dev_lock inside sco_connect, thus inverting the lock hierarchy. We fix this by pulling the call to hci_dev_lock out from sco_connect. Signed-off-by: Desmond Cheong Zhi Xi --- net/bluetooth/sco.c | 39 ++++++++++++++++----------------------- 1 file changed, 16 insertions(+), 23 deletions(-) diff --git a/net/bluetooth/sco.c b/net/bluetooth/sco.c index 62e638f971a9..94a3aa686556 100644 --- a/net/bluetooth/sco.c +++ b/net/bluetooth/sco.c @@ -237,44 +237,32 @@ static int sco_chan_add(struct sco_conn *conn, struct sock *sk, return err; } -static int sco_connect(struct sock *sk) +static int sco_connect(struct hci_dev *hdev, struct sock *sk) { struct sco_conn *conn; struct hci_conn *hcon; - struct hci_dev *hdev; int err, type; BT_DBG("%pMR -> %pMR", &sco_pi(sk)->src, &sco_pi(sk)->dst); - hdev = hci_get_route(&sco_pi(sk)->dst, &sco_pi(sk)->src, BDADDR_BREDR); - if (!hdev) - return -EHOSTUNREACH; - - hci_dev_lock(hdev); - if (lmp_esco_capable(hdev) && !disable_esco) type = ESCO_LINK; else type = SCO_LINK; if (sco_pi(sk)->setting == BT_VOICE_TRANSPARENT && - (!lmp_transp_capable(hdev) || !lmp_esco_capable(hdev))) { - err = -EOPNOTSUPP; - goto done; - } + (!lmp_transp_capable(hdev) || !lmp_esco_capable(hdev))) + return -EOPNOTSUPP; hcon = hci_connect_sco(hdev, type, &sco_pi(sk)->dst, sco_pi(sk)->setting); - if (IS_ERR(hcon)) { - err = PTR_ERR(hcon); - goto done; - } + if (IS_ERR(hcon)) + return PTR_ERR(hcon); conn = sco_conn_add(hcon); if (!conn) { hci_conn_drop(hcon); - err = -ENOMEM; - goto done; + return -ENOMEM; } /* Update source addr of the socket */ @@ -282,7 +270,7 @@ static int sco_connect(struct sock *sk) err = sco_chan_add(conn, sk, NULL); if (err) - goto done; + return err; if (hcon->state == BT_CONNECTED) { sco_sock_clear_timer(sk); @@ -292,9 +280,6 @@ static int sco_connect(struct sock *sk) sco_sock_set_timer(sk, sk->sk_sndtimeo); } -done: - hci_dev_unlock(hdev); - hci_dev_put(hdev); return err; } @@ -589,6 +574,7 @@ static int sco_sock_connect(struct socket *sock, struct sockaddr *addr, int alen { struct sockaddr_sco *sa = (struct sockaddr_sco *) addr; struct sock *sk = sock->sk; + struct hci_dev *hdev; int err; BT_DBG("sk %p", sk); @@ -603,12 +589,19 @@ static int sco_sock_connect(struct socket *sock, struct sockaddr *addr, int alen if (sk->sk_type != SOCK_SEQPACKET) return -EINVAL; + hdev = hci_get_route(&sa->sco_bdaddr, &sco_pi(sk)->src, BDADDR_BREDR); + if (!hdev) + return -EHOSTUNREACH; + hci_dev_lock(hdev); + lock_sock(sk); /* Set destination address and psm */ bacpy(&sco_pi(sk)->dst, &sa->sco_bdaddr); - err = sco_connect(sk); + err = sco_connect(hdev, sk); + hci_dev_unlock(hdev); + hci_dev_put(hdev); if (err) goto done; -- 2.25.1 _______________________________________________ Linux-kernel-mentees mailing list Linux-kernel-mentees@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees