WARNING in __bfs (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 59456c9cc40c Linux 4.19.204
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=14ac4b79300000
kernel config: https://syzkaller.appspot.com/x/.config?x=a84b4514346e13dc
dashboard link: https://syzkaller.appspot.com/bug?extid=45bc5134934d5b336d2f
compiler: gcc version 10.2.1 20210110 (Debian 10.2.1-6)

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+45bc51...@syzkaller.appspotmail.com

FAT-fs (loop5): invalid media value (0x00)
FAT-fs (loop5): Can't find a valid FAT filesystem
------------[ cut here ]------------
WARNING: CPU: 1 PID: 9142 at kernel/locking/lockdep.c:966 lock_accessed kernel/locking/lockdep.c:966 [inline]
WARNING: CPU: 1 PID: 9142 at kernel/locking/lockdep.c:966 __bfs.part.0.cold+0x11/0xeb kernel/locking/lockdep.c:1033
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 9142 Comm: kworker/1:3 Not tainted 4.19.204-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events l2cap_chan_timeout
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
panic+0x26a/0x50e kernel/panic.c:186
__warn.cold+0x20/0x5a kernel/panic.c:541
report_bug+0x262/0x2b0 lib/bug.c:183
fixup_bug arch/x86/kernel/traps.c:178 [inline]
fixup_bug arch/x86/kernel/traps.c:173 [inline]
do_error_trap+0x1d7/0x310 arch/x86/kernel/traps.c:296
invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:1038
RIP: 0010:lock_accessed kernel/locking/lockdep.c:966 [inline]
RIP: 0010:__bfs.part.0.cold+0x11/0xeb kernel/locking/lockdep.c:1033
Code: 60 27 24 8d e8 31 6c a5 f9 eb 88 48 c7 c7 40 e7 36 8d e8 23 6c a5 f9 eb bd 48 c7 c7 e0 1d 6a 88 48 89 54 24 20 e8 a6 87 00 00 <0f> 0b 49 8d 46 10 48 8b 54 24 20 48 89 44 24 18 48 c1 e8 03 42 80
RSP: 0018:ffff8880480cf770 EFLAGS: 00010086
RAX: 0000000000000024 RBX: ffffffff8cf03660 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff814e0d61 RDI: ffffed1009019ee0
RBP: ffff8880480cf828 R08: 0000000000000024 R09: 0000000000000000
R10: 0000000000000005 R11: ffffffff8c66405b R12: ffffffff814a80f0
R13: 0000000000000000 R14: 0000000000000000 R15: dffffc0000000000
__bfs kernel/locking/lockdep.c:1388 [inline]
__bfs_backwards kernel/locking/lockdep.c:1070 [inline]
find_usage_backwards kernel/locking/lockdep.c:1388 [inline]
check_usage_backwards+0x17a/0x300 kernel/locking/lockdep.c:2669
mark_lock_irq kernel/locking/lockdep.c:2760 [inline]
mark_lock+0x3d8/0x1160 kernel/locking/lockdep.c:3132
mark_irqflags kernel/locking/lockdep.c:3024 [inline]
__lock_acquire+0x63f/0x3ff0 kernel/locking/lockdep.c:3373
lock_acquire+0x170/0x3c0 kernel/locking/lockdep.c:3908
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline]
_raw_spin_lock_bh+0x2f/0x40 kernel/locking/spinlock.c:168
spin_lock_bh include/linux/spinlock.h:334 [inline]
lock_sock_nested+0x3b/0x110 net/core/sock.c:2864
l2cap_sock_teardown_cb+0xa0/0x6d0 net/bluetooth/l2cap_sock.c:1348
l2cap_chan_del+0xbc/0xa50 net/bluetooth/l2cap_core.c:603
l2cap_chan_close+0x1b5/0x950 net/bluetooth/l2cap_core.c:761
l2cap_chan_timeout+0x17e/0x2f0 net/bluetooth/l2cap_core.c:430
process_one_work+0x864/0x1570 kernel/workqueue.c:2153
worker_thread+0x64c/0x1130 kernel/workqueue.c:2296
kthread+0x33f/0x460 kernel/kthread.c:259
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415
Shutting down cpus with NMI
Kernel Offset: disabled
Rebooting in 86400 seconds..
----------------
Code disassembly (best guess), 2 bytes skipped:
0: 24 8d and $0x8d,%al
2: e8 31 6c a5 f9 callq 0xf9a56c38
7: eb 88 jmp 0xffffff91
9: 48 c7 c7 40 e7 36 8d mov $0xffffffff8d36e740,%rdi
10: e8 23 6c a5 f9 callq 0xf9a56c38
15: eb bd jmp 0xffffffd4
17: 48 c7 c7 e0 1d 6a 88 mov $0xffffffff886a1de0,%rdi
1e: 48 89 54 24 20 mov %rdx,0x20(%rsp)
23: e8 a6 87 00 00 callq 0x87ce
28: 0f 0b ud2 <-- trapping instruction
2a: 49 8d 46 10 lea 0x10(%r14),%rax
2e: 48 8b 54 24 20 mov 0x20(%rsp),%rdx
33: 48 89 44 24 18 mov %rax,0x18(%rsp)
38: 48 c1 e8 03 shr $0x3,%rax
3c: 42 rex.X
3d: 80 .byte 0x80


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.