734bc5ff78
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 <desmondcheongzx@gmail.com> Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.