Re: [syzbot] [nfc?] [net?] WARNING in nfc_rfkill_set_block

[Hillf Danton <hdanton@sina.com>]

On Thu, 14 Aug 2025 16:05:30 -0700
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    8f5ae30d69d7 Linux 6.17-rc1
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=16c80af0580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=13f39c6a0380a209
> dashboard link: https://syzkaller.appspot.com/bug?extid=535bbe83dfc3ae8d4be3
> compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/46150b6d2447/disk-8f5ae30d.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/1c604b2b2258/vmlinux-8f5ae30d.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/9c542f0972de/bzImage-8f5ae30d.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+535bbe83dfc3ae8d4be3@syzkaller.appspotmail.com
> 
> ------------[ cut here ]------------
> rtmutex deadlock detected

Even given the lockdep_set_novalidate_class() in device_initialize(),
rtmutex can detect deadlock (the ABBA one [1]?), weird.

[1] Subject: [PATCH] net/nfc: Fix A-B/B-A deadlock between nfc_unregister_device and rfkill_fop_write
https://lore.kernel.org/lkml/20250814173142.632749-2-ysk@kzalloc.com/

> WARNING: CPU: 1 PID: 9725 at kernel/locking/rtmutex.c:1674 rt_mutex_handle_deadlock+0x28/0xb0 kernel/locking/rtmutex.c:1674
> Modules linked in:
> CPU: 1 UID: 0 PID: 9725 Comm: syz.8.874 Tainted: G        W           6.17.0-rc1-syzkaller #0 PREEMPT_{RT,(full)} 
> Tainted: [W]=WARN
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
> RIP: 0010:rt_mutex_handle_deadlock+0x28/0xb0 kernel/locking/rtmutex.c:1674
> Code: 90 90 41 57 41 56 41 55 41 54 53 83 ff dd 0f 85 8c 00 00 00 48 89 f7 e8 c6 2c 01 00 90 48 c7 c7 a0 08 0b 8b e8 79 08 8b f6 90 <0f> 0b 90 90 4c 8d 3d 00 00 00 00 65 48 8b 1c 25 08 b0 f5 91 4c 8d
> RSP: 0018:ffffc900043a7950 EFLAGS: 00010246
> RAX: 89021558f1df5a00 RBX: ffffc900043a79e0 RCX: ffff888025bb3b80
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: ffffc900043a7b00 R08: 0000000000000000 R09: 0000000000000000
> R10: dffffc0000000000 R11: ffffed1017124863 R12: 1ffff92000874f38
> R13: ffffffff8af82119 R14: ffff888036e55098 R15: dffffc0000000000
> FS:  00007fec70d5e6c0(0000) GS:ffff8881269c5000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fce013b0000 CR3: 000000003ebbc000 CR4: 00000000003526f0
> Call Trace:
>  <TASK>
>  __rt_mutex_slowlock kernel/locking/rtmutex.c:1734 [inline]
>  __rt_mutex_slowlock_locked kernel/locking/rtmutex.c:1760 [inline]
>  rt_mutex_slowlock+0x692/0x6e0 kernel/locking/rtmutex.c:1800
>  __rt_mutex_lock kernel/locking/rtmutex.c:1815 [inline]
>  __mutex_lock_common kernel/locking/rtmutex_api.c:536 [inline]
>  mutex_lock_nested+0x16a/0x1d0 kernel/locking/rtmutex_api.c:547
>  device_lock include/linux/device.h:911 [inline]
>  nfc_dev_down net/nfc/core.c:143 [inline]
>  nfc_rfkill_set_block+0x50/0x2e0 net/nfc/core.c:179
>  rfkill_set_block+0x1e5/0x450 net/rfkill/core.c:346
>  rfkill_fop_write+0x44e/0x580 net/rfkill/core.c:1301
>  vfs_write+0x287/0xb40 fs/read_write.c:684
>  ksys_write+0x14b/0x260 fs/read_write.c:738
>  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>  do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fec72afebe9
> 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:00007fec70d5e038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> RAX: ffffffffffffffda RBX: 00007fec72d25fa0 RCX: 00007fec72afebe9
> RDX: 0000000000000008 RSI: 0000200000000080 RDI: 0000000000000003
> RBP: 00007fec72b81e19 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007fec72d26038 R14: 00007fec72d25fa0 R15: 00007ffe1f71d718
>  </TASK>
> 
> 
> ---
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