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AKwUvBwEmZ3EC6aAASTDJhUREmtIlFgilHy9av/gbOnT+ZlEdoCQMCiWuRakMKuFqzUl8pZD6yG0XzfPX/gHryI=@vger.kernel.org X-Gm-Message-State: AFuF++kiggdXTB+ZfrEsN6d7JHkAoZnJEdZsinkm0KPmKrz78+fZ5THx fKduRPlBR2be02/rfmIAszE5aslghF6vl+K7OIVbBTkhWR/rzBZ6wSzLEJzeZVK6rfR3NYypTTW +OXlV2KitzZGaGk0fAF7XGEoTARGUZYCKz8np4EYRtMm6MprVbh/ECPncVZQ= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6808:6807:b0:4b9:e5fa:8a1d with SMTP id 5614622812f47-4b9e5fa8f23mr25474168b6e.34.1789056574511; Thu, 10 Sep 2026 09:09:34 -0700 (PDT) Date: Thu, 10 Sep 2026 09:09:34 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6aa2d63e.6e6c5f9e.28f11f.0036.GAE@google.com> Subject: [syzbot] [bluetooth?] possible deadlock in rfcomm_dlc_close 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: 50d05c7c76c9 Merge tag 'landlock-7.3-rc3' of git://git.ker.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=15ad0905580000 kernel config: https://syzkaller.appspot.com/x/.config?x=8c5c3949d762a91f dashboard link: https://syzkaller.appspot.com/bug?extid=0cece8fa7d83523f47a3 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=13ad0905580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12752c8e580000 Downloadable assets: disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-50d05c7c.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/6f77d29903f3/vmlinux-50d05c7c.xz kernel image: https://storage.googleapis.com/syzbot-assets/23b2961d9c5d/bzImage-50d05c7c.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+0cece8fa7d83523f47a3@syzkaller.appspotmail.com ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.0.67/5982 is trying to acquire lock: ffffffff90f80f40 (rfcomm_mutex){+.+.}-{4:4}, at: rfcomm_dlc_close+0x33/0x240 net/bluetooth/rfcomm/core.c:508 but task is already holding lock: ffff8880234b9260 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1713 [inline] ffff8880234b9260 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_close net/bluetooth/rfcomm/sock.c:245 [inline] ffff8880234b9260 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_cleanup_listen net/bluetooth/rfcomm/sock.c:190 [inline] ffff8880234b9260 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: __rfcomm_sock_close+0x1c3/0x300 net/bluetooth/rfcomm/sock.c:224 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}: lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 lock_sock_nested+0x41/0xf0 net/core/sock.c:3830 lock_sock include/net/sock.h:1713 [inline] rfcomm_connect_ind+0x327/0x9e0 net/bluetooth/rfcomm/sock.c:968 rfcomm_recv_pn net/bluetooth/rfcomm/core.c:1509 [inline] rfcomm_recv_mcc net/bluetooth/rfcomm/core.c:1727 [inline] rfcomm_recv_frame net/bluetooth/rfcomm/core.c:1868 [inline] rfcomm_process_rx net/bluetooth/rfcomm/core.c:2020 [inline] rfcomm_process_sessions net/bluetooth/rfcomm/core.c:2114 [inline] rfcomm_run+0x438b/0x54c0 net/bluetooth/rfcomm/core.c:2204 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 (rfcomm_mutex){+.+.}-{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 rfcomm_dlc_close+0x33/0x240 net/bluetooth/rfcomm/core.c:508 __rfcomm_sock_close+0x181/0x300 net/bluetooth/rfcomm/sock.c:231 rfcomm_sock_close net/bluetooth/rfcomm/sock.c:246 [inline] rfcomm_sock_cleanup_listen net/bluetooth/rfcomm/sock.c:190 [inline] __rfcomm_sock_close+0x1d2/0x300 net/bluetooth/rfcomm/sock.c:224 rfcomm_sock_shutdown+0x111/0x250 net/bluetooth/rfcomm/sock.c:920 rfcomm_sock_release+0x61/0x1a0 net/bluetooth/rfcomm/sock.c:941 __sock_release+0xb3/0x260 net/socket.c:735 sock_close+0x1c/0x30 net/socket.c:1526 __fput+0x3ff/0xb50 fs/file_table.c:512 task_work_run+0x150/0x240 kernel/task_work.c:233 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] __exit_to_user_mode_loop kernel/entry/common.c:70 [inline] exit_to_user_mode_loop+0x1d8/0x700 kernel/entry/common.c:101 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline] syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline] syscall_exit_to_user_mode include/linux/entry-common.h:336 [inline] do_syscall_64+0x661/0x790 arch/x86/entry/syscall_64.c:89 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM); lock(rfcomm_mutex); lock(sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM); lock(rfcomm_mutex); *** DEADLOCK *** locks held by syz.0.67/5982: 2, last CPU#0: #0: ffff88805501bbc0 (&sb->s_type->i_mutex_key#13){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1024 [inline] #0: ffff88805501bbc0 (&sb->s_type->i_mutex_key#13){+.+.}-{4:4}, at: __sock_release+0x86/0x260 net/socket.c:734 #1: ffff8880234b9260 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1713 [inline] #1: ffff8880234b9260 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_close net/bluetooth/rfcomm/sock.c:245 [inline] #1: ffff8880234b9260 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_cleanup_listen net/bluetooth/rfcomm/sock.c:190 [inline] #1: ffff8880234b9260 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: __rfcomm_sock_close+0x1c3/0x300 net/bluetooth/rfcomm/sock.c:224 stack backtrace: CPU: 0 UID: 0 PID: 5982 Comm: syz.0.67 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 rfcomm_dlc_close+0x33/0x240 net/bluetooth/rfcomm/core.c:508 __rfcomm_sock_close+0x181/0x300 net/bluetooth/rfcomm/sock.c:231 rfcomm_sock_close net/bluetooth/rfcomm/sock.c:246 [inline] rfcomm_sock_cleanup_listen net/bluetooth/rfcomm/sock.c:190 [inline] __rfcomm_sock_close+0x1d2/0x300 net/bluetooth/rfcomm/sock.c:224 rfcomm_sock_shutdown+0x111/0x250 net/bluetooth/rfcomm/sock.c:920 rfcomm_sock_release+0x61/0x1a0 net/bluetooth/rfcomm/sock.c:941 __sock_release+0xb3/0x260 net/socket.c:735 sock_close+0x1c/0x30 net/socket.c:1526 __fput+0x3ff/0xb50 fs/file_table.c:512 task_work_run+0x150/0x240 kernel/task_work.c:233 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] __exit_to_user_mode_loop kernel/entry/common.c:70 [inline] exit_to_user_mode_loop+0x1d8/0x700 kernel/entry/common.c:101 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline] syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline] syscall_exit_to_user_mode include/linux/entry-common.h:336 [inline] do_syscall_64+0x661/0x790 arch/x86/entry/syscall_64.c:89 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fd18819e159 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:00007ffe0b172838 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4 RAX: 0000000000000000 RBX: 00007ffe0b172920 RCX: 00007fd18819e159 RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003 RBP: 000000000000e138 R08: 0000000000000001 R09: 0000000000000000 R10: 0000001b32a20000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fd188425fac R14: 00007fd188425fa8 R15: 00007fd188425fa0 --- This report is generated by a bot. 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