[syzbot] [net?] [nfc?] WARNING in nfc_dev_down

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d358e5254674 Merge tag 'for-6.19/dm-changes' of git://git...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13b2961a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f315601b98a91c0b
dashboard link: https://syzkaller.appspot.com/bug?extid=4ef89409a235d804c6c2
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/def5abdae246/disk-d358e525.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/171af6e9cc68/vmlinux-d358e525.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2342dcd05182/bzImage-d358e525.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4ef894...@syzkaller.appspotmail.com

------------[ cut here ]------------
rtmutex deadlock detected
WARNING: kernel/locking/rtmutex.c:1674 at 0x0, CPU#1: syz.4.2932/13586
Modules linked in:
CPU: 1 UID: 0 PID: 13586 Comm: syz.4.2932 Tainted: G L syzkaller #0 PREEMPT_{RT,(full)}
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:rt_mutex_handle_deadlock+0x21/0xb0 kernel/locking/rtmutex.c:1674
Code: 90 90 90 90 90 90 90 90 90 41 57 41 56 41 55 41 54 53 83 ff dd 0f 85 86 00 00 00 48 89 f7 e8 66 3b 01 00 48 8d 3d cf eb 08 04 <67> 48 0f b9 3a 4c 8d 3d 00 00 00 00 65 48 8b 1c 25 08 a0 b1 91 4c
RSP: 0018:ffffc900040d78b0 EFLAGS: 00010286
RAX: 0000000080000000 RBX: ffffc900040d7940 RCX: 0000000000000000
RDX: 0000000000000006 RSI: ffffffff8ce093ac RDI: ffffffff8ede2bf0
RBP: ffffc900040d7a58 R08: ffffffff8edb0977 R09: 1ffffffff1db612e
R10: dffffc0000000000 R11: fffffbfff1db612f R12: 1ffff9200081af24
R13: ffffffff8ad53b09 R14: ffff8880382f9098 R15: dffffc0000000000
FS: 00007f35de10c6c0(0000) GS:ffff888126e06000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055558f47b588 CR3: 0000000063c72000 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+0x666/0x6b0 kernel/locking/rtmutex.c:1800
__rt_mutex_lock kernel/locking/rtmutex.c:1815 [inline]
__mutex_lock_common kernel/locking/rtmutex_api.c:534 [inline]
mutex_lock_nested+0x16a/0x1d0 kernel/locking/rtmutex_api.c:552
device_lock include/linux/device.h:895 [inline]
nfc_dev_down+0x3b/0x290 net/nfc/core.c:143
nfc_rfkill_set_block+0x2d/0x100 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
do_loop_readv_writev fs/read_write.c:850 [inline]
vfs_writev+0x4bf/0x970 fs/read_write.c:1059
do_writev+0x153/0x2d0 fs/read_write.c:1103
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f35dfeef749
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:00007f35de10c038 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 00007f35e0146180 RCX: 00007f35dfeef749
RDX: 0000000000000001 RSI: 0000200000000500 RDI: 0000000000000004
RBP: 00007f35dff73f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f35e0146218 R14: 00007f35e0146180 R15: 00007ffd7e110468
</TASK>
----------------
Code disassembly (best guess):
0: 90 nop
1: 90 nop
2: 90 nop
3: 90 nop
4: 90 nop
5: 90 nop
6: 90 nop
7: 90 nop
8: 90 nop
9: 41 57 push %r15
b: 41 56 push %r14
d: 41 55 push %r13
f: 41 54 push %r12
11: 53 push %rbx
12: 83 ff dd cmp $0xffffffdd,%edi
15: 0f 85 86 00 00 00 jne 0xa1
1b: 48 89 f7 mov %rsi,%rdi
1e: e8 66 3b 01 00 call 0x13b89
23: 48 8d 3d cf eb 08 04 lea 0x408ebcf(%rip),%rdi # 0x408ebf9
* 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction
2f: 4c 8d 3d 00 00 00 00 lea 0x0(%rip),%r15 # 0x36
36: 65 48 8b 1c 25 08 a0 mov %gs:0xffffffff91b1a008,%rbx
3d: b1 91
3f: 4c rex.WR


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 8f0b4cce4481 Linux 6.19-rc1
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=102035c2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=1f2b6fe1fdf1a00b

dashboard link: https://syzkaller.appspot.com/bug?extid=4ef89409a235d804c6c2
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1101b91a580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=142035c2580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ea3b19e4d883/disk-8f0b4cce.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bd7c115820ba/vmlinux-8f0b4cce.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e5813cc1963f/bzImage-8f0b4cce.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4ef894...@syzkaller.appspotmail.com

------------[ cut here ]------------
rtmutex deadlock detected

WARNING: kernel/locking/rtmutex.c:1674 at rt_mutex_handle_deadlock+0x21/0xb0 kernel/locking/rtmutex.c:1674, CPU#1: syz.3.31/6310
Modules linked in:
CPU: 1 UID: 0 PID: 6310 Comm: syz.3.31 Not tainted syzkaller #0 PREEMPT_{RT,(full)}

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:rt_mutex_handle_deadlock+0x21/0xb0 kernel/locking/rtmutex.c:1674

Code: 90 90 90 90 90 90 90 90 90 41 57 41 56 41 55 41 54 53 83 ff dd 0f 85 86 00 00 00 48 89 f7 e8 66 3b 01 00 48 8d 3d 6f 83 08 04 <67> 48 0f b9 3a 4c 8d 3d 00 00 00 00 65 48 8b 1c 25 08 d0 b1 91 4c
RSP: 0018:ffffc90004d97930 EFLAGS: 00010286
RAX: 0000000080000000 RBX: ffffc90004d979c0 RCX: 0000000000000000
RDX: 0000000000000006 RSI: ffffffff8ce0bc0c RDI: ffffffff8ede53f0
RBP: ffffc90004d97ad8 R08: ffffffff8edb3177 R09: 1ffffffff1db662e
R10: dffffc0000000000 R11: fffffbfff1db662f R12: 1ffff920009b2f34
R13: ffffffff8ad5cb69 R14: ffff888037dc6098 R15: dffffc0000000000
FS: 000055557d26b500(0000) GS:ffff888126e03000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 00007ffcf0a37f52 CR3: 00000000329d0000 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+0x666/0x6b0 kernel/locking/rtmutex.c:1800
__rt_mutex_lock kernel/locking/rtmutex.c:1815 [inline]
__mutex_lock_common kernel/locking/rtmutex_api.c:534 [inline]
mutex_lock_nested+0x16a/0x1d0 kernel/locking/rtmutex_api.c:552
device_lock include/linux/device.h:895 [inline]
nfc_dev_down+0x3b/0x290 net/nfc/core.c:143
nfc_rfkill_set_block+0x2d/0x100 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/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

RIP: 0033:0x7f28f61cf749

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:00007fffd96926f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f28f6425fa0 RCX: 00007f28f61cf749
RDX: 0000000000000008 RSI: 0000200000000080 RDI: 0000000000000004
RBP: 00007f28f6253f91 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007f28f6425fa0 R14: 00007f28f6425fa0 R15: 0000000000000003

</TASK>
----------------
Code disassembly (best guess):
0: 90 nop
1: 90 nop
2: 90 nop
3: 90 nop
4: 90 nop
5: 90 nop
6: 90 nop
7: 90 nop
8: 90 nop
9: 41 57 push %r15
b: 41 56 push %r14
d: 41 55 push %r13
f: 41 54 push %r12
11: 53 push %rbx
12: 83 ff dd cmp $0xffffffdd,%edi
15: 0f 85 86 00 00 00 jne 0xa1
1b: 48 89 f7 mov %rsi,%rdi
1e: e8 66 3b 01 00 call 0x13b89

23: 48 8d 3d 6f 83 08 04 lea 0x408836f(%rip),%rdi # 0x4088399

* 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction
2f: 4c 8d 3d 00 00 00 00 lea 0x0(%rip),%r15 # 0x36

36: 65 48 8b 1c 25 08 d0 mov %gs:0xffffffff91b1d008,%rbx

3d: b1 91
3f: 4c rex.WR


---

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