linux-kernel - [syzbot] [bluetooth?] WARNING in hci_devcd

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Message-ID: <689efe71.050a0220.e29e5.0012.GAE@google.com>
Date: Fri, 15 Aug 2025 02:31:29 -0700
From: syzbot <syzbot+5f1a55873cde03ffb993@...kaller.appspotmail.com>
To: johan.hedberg@...il.com, linux-bluetooth@...r.kernel.org, 
	linux-kernel@...r.kernel.org, luiz.dentz@...il.com, marcel@...tmann.org, 
	syzkaller-bugs@...glegroups.com
Subject: [syzbot] [bluetooth?] WARNING in hci_devcd_register (2)

Hello,

syzbot found the following issue on:

HEAD commit:    8742b2d8935f Merge tag 'pull-fixes' of git://git.kernel.or..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=173325a2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=fc3f2c190ebad30b
dashboard link: https://syzkaller.appspot.com/bug?extid=5f1a55873cde03ffb993
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ef8eda74e1e8/disk-8742b2d8.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/193376a0f0a4/vmlinux-8742b2d8.xz
kernel image: https://storage.googleapis.com/syzbot-assets/fadbd8800c02/bzImage-8742b2d8.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5f1a55873cde03ffb993@...kaller.appspotmail.com

------------[ cut here ]------------
DEBUG_LOCKS_WARN_ON(lock->magic != lock)
WARNING: CPU: 0 PID: 17040 at kernel/locking/mutex.c:577 __mutex_lock_common kernel/locking/mutex.c:577 [inline]
WARNING: CPU: 0 PID: 17040 at kernel/locking/mutex.c:577 __mutex_lock+0x39f/0x10b0 kernel/locking/mutex.c:760
Modules linked in:
CPU: 0 UID: 0 PID: 17040 Comm: syz.3.2558 Not tainted 6.17.0-rc1-syzkaller-00016-g8742b2d8935f #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:__mutex_lock_common kernel/locking/mutex.c:577 [inline]
RIP: 0010:__mutex_lock+0x39f/0x10b0 kernel/locking/mutex.c:760
Code: d0 7c 08 84 d2 0f 85 40 0c 00 00 8b 3d 5a cb 19 05 85 ff 75 19 90 48 c7 c6 40 55 ad 8b 48 c7 c7 80 54 ad 8b e8 32 2e e8 f5 90 <0f> 0b 90 90 90 e9 b8 fd ff ff 48 8d 85 60 ff ff ff 48 89 df 48 89
RSP: 0018:ffffc90004977a70 EFLAGS: 00010282
RAX: 0000000000000000 RBX: ffff888062872050 RCX: ffffc9000ffb6000
RDX: 0000000000080000 RSI: ffffffff817a02d5 RDI: 0000000000000001
RBP: ffffc90004977bc0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 284e4f5f4e524157 R12: dffffc0000000000
R13: 0000000000000000 R14: 1ffff9200092ef5a R15: ffffffff8a99e7b7
FS:  00007f23fca8e6c0(0000) GS:ffff8881246c6000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 00000000523fa000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 hci_devcd_register+0x47/0x170 net/bluetooth/coredump.c:433
 force_devcd_write+0x16c/0x340 drivers/bluetooth/hci_vhci.c:346
 full_proxy_write+0x131/0x1a0 fs/debugfs/file.c:388
 vfs_write+0x29d/0x11d0 fs/read_write.c:684
 ksys_write+0x12a/0x250 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f23fbb8ebe9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f23fca8e038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f23fbdb6180 RCX: 00007f23fbb8ebe9
RDX: 000000000000000e RSI: 0000000000000000 RDI: 0000000000000007
RBP: 00007f23fbc11e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f23fbdb6218 R14: 00007f23fbdb6180 R15: 00007ffc4456d828
 </TASK>


---
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