syzbot


BUG: unable to handle kernel paging request in kernfs_remove_by_name_ns

Status: moderation: reported on 2025/07/09 10:41
Subsystems: kernfs
[Documentation on labels]
Reported-by: syzbot+9e79574bfa567d87e303@syzkaller.appspotmail.com
First crash: 4d21h, last: 4d21h

Sample crash report:
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 0000000000000000 R14: 00007f65cabb5fa0 R15: 00007ffeded21b78
 </TASK>
comedi comedi1: c6xdigio: I/O port conflict (0x8001,3)
BUG: unable to handle page fault for address: ffffffff9b3fc110
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD e33b067 P4D e33b067 PUD e33c063 PMD 0 
Oops: Oops: 0000 [#1] SMP KASAN PTI
CPU: 1 UID: 0 PID: 17928 Comm: syz.1.2931 Not tainted 6.16.0-rc4-next-20250704-syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:variable_test_bit arch/x86/include/asm/bitops.h:227 [inline]
RIP: 0010:arch_test_bit arch/x86/include/asm/bitops.h:239 [inline]
RIP: 0010:_test_bit include/asm-generic/bitops/instrumented-non-atomic.h:142 [inline]
RIP: 0010:__lock_acquire+0x6c1/0xd20 kernel/locking/lockdep.c:5210
Code: b3 00 00 00 4c 89 f6 ba 08 00 00 00 e8 88 25 00 00 45 31 ff 85 c0 0f 84 f5 05 00 00 83 3d d6 51 54 18 00 75 13 48 63 44 24 20 <48> 0f a3 05 67 c2 50 12 0f 83 15 05 00 00 31 ed 48 8b 3c 24 4c 8b
RSP: 0018:ffffc90004d07810 EFLAGS: 00010046
RAX: 000000003a87ec9b RBX: ffff888029f5bc00 RCX: ffffffff93999c08
RDX: 0000000000000008 RSI: ffff888029f5c768 RDI: ffff888029f5bc00
RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff825fb67d
R10: dffffc0000000000 R11: ffffed1003bd6a23 R12: 0000000000000004
R13: 0000000000000004 R14: ffff888029f5c768 R15: 0000000000000000
FS:  00007f65cb87b6c0(0000) GS:ffff8881258af000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffff9b3fc110 CR3: 0000000030b30000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
 down_write+0x96/0x1f0 kernel/locking/rwsem.c:1577
 kernfs_remove_by_name_ns+0x3d/0x130 fs/kernfs/dir.c:1712
 remove_bind_files drivers/base/bus.c:605 [inline]
 bus_remove_driver+0x198/0x2f0 drivers/base/bus.c:743
 comedi_device_detach+0x134/0x720 drivers/comedi/drivers.c:207
 comedi_device_attach+0x568/0x670 drivers/comedi/drivers.c:1000
 do_devconfig_ioctl drivers/comedi/comedi_fops.c:855 [inline]
 comedi_unlocked_ioctl+0x686/0xf40 drivers/comedi/comedi_fops.c:2136
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:598 [inline]
 __se_sys_ioctl+0xf9/0x170 fs/ioctl.c:584
 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: 0033:0x7f65ca98e929
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:00007f65cb87b038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f65cabb5fa0 RCX: 00007f65ca98e929
RDX: 0000200000000100 RSI: 0000000040946400 RDI: 0000000000000003
RBP: 00007f65cb87b090 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 0000000000000000 R14: 00007f65cabb5fa0 R15: 00007ffeded21b78
 </TASK>
Modules linked in:
CR2: ffffffff9b3fc110
---[ end trace 0000000000000000 ]---
RIP: 0010:variable_test_bit arch/x86/include/asm/bitops.h:227 [inline]
RIP: 0010:arch_test_bit arch/x86/include/asm/bitops.h:239 [inline]
RIP: 0010:_test_bit include/asm-generic/bitops/instrumented-non-atomic.h:142 [inline]
RIP: 0010:__lock_acquire+0x6c1/0xd20 kernel/locking/lockdep.c:5210
Code: b3 00 00 00 4c 89 f6 ba 08 00 00 00 e8 88 25 00 00 45 31 ff 85 c0 0f 84 f5 05 00 00 83 3d d6 51 54 18 00 75 13 48 63 44 24 20 <48> 0f a3 05 67 c2 50 12 0f 83 15 05 00 00 31 ed 48 8b 3c 24 4c 8b
RSP: 0018:ffffc90004d07810 EFLAGS: 00010046
RAX: 000000003a87ec9b RBX: ffff888029f5bc00 RCX: ffffffff93999c08
RDX: 0000000000000008 RSI: ffff888029f5c768 RDI: ffff888029f5bc00
RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff825fb67d
R10: dffffc0000000000 R11: ffffed1003bd6a23 R12: 0000000000000004
R13: 0000000000000004 R14: ffff888029f5c768 R15: 0000000000000000
FS:  00007f65cb87b6c0(0000) GS:ffff8881258af000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffff9b3fc110 CR3: 0000000030b30000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
   0:	b3 00                	mov    $0x0,%bl
   2:	00 00                	add    %al,(%rax)
   4:	4c 89 f6             	mov    %r14,%rsi
   7:	ba 08 00 00 00       	mov    $0x8,%edx
   c:	e8 88 25 00 00       	call   0x2599
  11:	45 31 ff             	xor    %r15d,%r15d
  14:	85 c0                	test   %eax,%eax
  16:	0f 84 f5 05 00 00    	je     0x611
  1c:	83 3d d6 51 54 18 00 	cmpl   $0x0,0x185451d6(%rip)        # 0x185451f9
  23:	75 13                	jne    0x38
  25:	48 63 44 24 20       	movslq 0x20(%rsp),%rax
* 2a:	48 0f a3 05 67 c2 50 	bt     %rax,0x1250c267(%rip)        # 0x1250c299 <-- trapping instruction
  31:	12
  32:	0f 83 15 05 00 00    	jae    0x54d
  38:	31 ed                	xor    %ebp,%ebp
  3a:	48 8b 3c 24          	mov    (%rsp),%rdi
  3e:	4c                   	rex.WR
  3f:	8b                   	.byte 0x8b

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/07/05 10:31 linux-next 26ffb3d6f02c 4f67c4ae .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce BUG: unable to handle kernel paging request in kernfs_remove_by_name_ns
* Struck through repros no longer work on HEAD.