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AKwUvBwAK/LcSD7hB8ppp/xDOlNvHj4VIltr8ttQIF9+MgllMOs4MM1n7rgDBpyPE+IE6dYlQVWzqMqz4zc0FRk=@vger.kernel.org X-Gm-Message-State: AFuF++meKSRCEp1mYSNm6WbWjsZAthzDsGQbJaYtOk8g2mY9jn3fmuN0 W1KMgKld8f3cxgazllwvVKbWl1V08mMjAaaaLIwYkSWEwjBpSx3zbyqoGCqxkOQIFT9NkN+93O2 usAMecK5ah0+0JYmvPT378N2m65LQk2qUL7aRcs+jRpLyLzFlwkDHn0ycqh4= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6808:2384:b0:4e5:c2b4:33a3 with SMTP id 5614622812f47-4fb415d61e1mr1585684b6e.45.1791303565794; Tue, 06 Oct 2026 09:19:25 -0700 (PDT) Date: Tue, 06 Oct 2026 09:19:25 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6ac51f8d.353c8d8e.177895.0006.GAE@google.com> Subject: [syzbot] [bluetooth?] possible deadlock in l2cap_chan_connect (2) From: syzbot To: linux-bluetooth@vger.kernel.org, linux-kernel@vger.kernel.org, luiz.dentz@gmail.com, marcel@holtmann.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: 2c3418fffa9d Merge tag 'keys-v7.3-rc7' of git://git.kernel.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=17ca6ff5580000 kernel config: https://syzkaller.appspot.com/x/.config?x=929e4854a828f434 dashboard link: https://syzkaller.appspot.com/bug?extid=1fed874be1d7e459b5a3 compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=101e6f25580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13cfbff5580000 Downloadable assets: disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-2c3418ff.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/1818dc9d2f44/vmlinux-2c3418ff.xz kernel image: https://storage.googleapis.com/syzbot-assets/52ad1b5b053d/bzImage-2c3418ff.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+1fed874be1d7e459b5a3@syzkaller.appspotmail.com ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.0.17/5921 is trying to acquire lock: ffff88802d8700b8 (&hdev->lock){+.+.}-{4:4}, at: l2cap_chan_connect+0xac/0x2110 net/bluetooth/l2cap_core.c:7289 but task is already holding lock: ffffffff90f83f60 (rfcomm_mutex){+.+.}-{4:4}, at: rfcomm_dlc_open+0x92/0xac0 net/bluetooth/rfcomm/core.c:426 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (rfcomm_mutex){+.+.}-{4:4}: lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821 rfcomm_security_cfm+0x3f/0x4b0 net/bluetooth/rfcomm/core.c:2223 hci_auth_cfm include/net/bluetooth/hci_core.h:2203 [inline] hci_auth_complete_evt+0x811/0x1180 net/bluetooth/hci_event.c:3554 hci_event_func net/bluetooth/hci_event.c:7887 [inline] hci_event_packet+0x8e9/0xcd0 net/bluetooth/hci_event.c:7938 hci_rx_work+0x451/0xfc0 net/bluetooth/hci_core.c:4087 process_one_work+0xac7/0x1b10 kernel/workqueue.c:3396 process_scheduled_works kernel/workqueue.c:3479 [inline] worker_thread+0x5ef/0xe50 kernel/workqueue.c:3560 kthread+0x373/0x450 kernel/kthread.c:436 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #1 (hci_cb_list_lock){+.+.}-{4:4}: lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821 hci_connect_cfm include/net/bluetooth/hci_core.h:2164 [inline] hci_remote_features_evt+0x485/0x9b0 net/bluetooth/hci_event.c:3786 hci_event_func net/bluetooth/hci_event.c:7887 [inline] hci_event_packet+0x8e9/0xcd0 net/bluetooth/hci_event.c:7938 hci_rx_work+0x451/0xfc0 net/bluetooth/hci_core.c:4087 process_one_work+0xac7/0x1b10 kernel/workqueue.c:3396 process_scheduled_works kernel/workqueue.c:3479 [inline] worker_thread+0x5ef/0xe50 kernel/workqueue.c:3560 kthread+0x373/0x450 kernel/kthread.c:436 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #0 (&hdev->lock){+.+.}-{4:4}: check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3209 check_prevs_add kernel/locking/lockdep.c:3328 [inline] validate_chain kernel/locking/lockdep.c:3952 [inline] __lock_acquire+0x1528/0x1f40 kernel/locking/lockdep.c:5288 lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821 l2cap_chan_connect+0xac/0x2110 net/bluetooth/l2cap_core.c:7289 l2cap_sock_connect+0x37a/0x770 net/bluetooth/l2cap_sock.c:255 kernel_connect+0x107/0x160 net/socket.c:3755 rfcomm_session_create net/bluetooth/rfcomm/core.c:808 [inline] __rfcomm_dlc_open net/bluetooth/rfcomm/core.c:385 [inline] rfcomm_dlc_open+0x838/0xac0 net/bluetooth/rfcomm/core.c:428 rfcomm_sock_connect+0x42c/0x690 net/bluetooth/rfcomm/sock.c:419 connect_socket net/socket.c:2141 [inline] connect_socket net/socket.c:2131 [inline] __sys_connect_file+0x146/0x1a0 net/socket.c:2166 __sys_connect+0x141/0x170 net/socket.c:2183 __do_sys_connect net/socket.c:2189 [inline] __se_sys_connect net/socket.c:2186 [inline] __x64_sys_connect+0x72/0xb0 net/socket.c:2186 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Chain exists of: &hdev->lock --> hci_cb_list_lock --> rfcomm_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(rfcomm_mutex); lock(hci_cb_list_lock); lock(rfcomm_mutex); lock(&hdev->lock); *** DEADLOCK *** locks held by syz.0.17/5921: 1, last CPU#3: #0: ffffffff90f83f60 (rfcomm_mutex){+.+.}-{4:4}, at: rfcomm_dlc_open+0x92/0xac0 net/bluetooth/rfcomm/core.c:426 stack backtrace: CPU: 3 UID: 0 PID: 5921 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120 print_circular_bug.cold+0x178/0x1be kernel/locking/lockdep.c:2087 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2219 check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3209 check_prevs_add kernel/locking/lockdep.c:3328 [inline] validate_chain kernel/locking/lockdep.c:3952 [inline] __lock_acquire+0x1528/0x1f40 kernel/locking/lockdep.c:5288 lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821 l2cap_chan_connect+0xac/0x2110 net/bluetooth/l2cap_core.c:7289 l2cap_sock_connect+0x37a/0x770 net/bluetooth/l2cap_sock.c:255 kernel_connect+0x107/0x160 net/socket.c:3755 rfcomm_session_create net/bluetooth/rfcomm/core.c:808 [inline] __rfcomm_dlc_open net/bluetooth/rfcomm/core.c:385 [inline] rfcomm_dlc_open+0x838/0xac0 net/bluetooth/rfcomm/core.c:428 rfcomm_sock_connect+0x42c/0x690 net/bluetooth/rfcomm/sock.c:419 connect_socket net/socket.c:2141 [inline] connect_socket net/socket.c:2131 [inline] __sys_connect_file+0x146/0x1a0 net/socket.c:2166 __sys_connect+0x141/0x170 net/socket.c:2183 __do_sys_connect net/socket.c:2189 [inline] __se_sys_connect net/socket.c:2186 [inline] __x64_sys_connect+0x72/0xb0 net/socket.c:2186 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fa5d1b9e199 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffc664cdb68 EFLAGS: 00000246 ORIG_RAX: 000000000000002a RAX: ffffffffffffffda RBX: 00007fa5d1e25fa0 RCX: 00007fa5d1b9e199 RDX: 000000000000000a RSI: 0000200000000040 RDI: 0000000000000004 RBP: 00007fa5d1c358e0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fa5d1e25fac R14: 00007fa5d1e25fa0 R15: 00007fa5d1e25fa0 --- This report is generated by a bot. 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