Re: [syzbot] [kernel?] general protection fault in device_move

[syzbot <syzbot+1f4e278e8e1a9b01f95f@syzkaller.appspotmail.com>]

syzbot has found a reproducer for the following issue on:

HEAD commit:    f9a2394a2348 Merge tag 'mm-hotfixes-stable-2026-08-06-18-4..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=101a02c6580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=86ba763b42fa66a
dashboard link: https://syzkaller.appspot.com/bug?extid=1f4e278e8e1a9b01f95f
compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=170d0fb9580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1f4e278e8e1a9b01f95f@syzkaller.appspotmail.com

Oops: general protection fault, probably for non-canonical address 0xdffffc000000000b: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000058-0x000000000000005f]
CPU: 1 UID: 0 PID: 4943 Comm: kworker/u9:1 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: hci0 hci_rx_work
RIP: 0010:klist_put lib/klist.c:212 [inline]
RIP: 0010:klist_del lib/klist.c:230 [inline]
RIP: 0010:klist_remove+0x156/0x340 lib/klist.c:249
Code: 4d 89 f5 49 c1 ed 03 43 80 7c 3d 00 00 74 08 4c 89 f7 e8 8d 64 84 f6 4d 8b 26 49 83 e4 fe 49 8d 7c 24 58 48 89 f8 48 c1 e8 03 <42> 80 3c 38 00 74 05 e8 6e 64 84 f6 49 8b 44 24 58 48 89 44 24 08
RSP: 0018:ffffc9000fc87700 EFLAGS: 00010202
RAX: 000000000000000b RBX: ffff888035a90000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000058
RBP: ffffc9000fc877e8 R08: ffffffff90199ae3 R09: 1ffffffff203335c
R10: dffffc0000000000 R11: fffffbfff203335d R12: 0000000000000000
R13: 1ffff1100e64e20c R14: ffff888073271060 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff888125306000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f4691400c30 CR3: 00000000750f0000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 device_move+0x18e/0x720 drivers/base/core.c:4698
 hci_conn_del_sysfs+0xb8/0x1a0 net/bluetooth/hci_sysfs.c:75
 hci_conn_cleanup net/bluetooth/hci_conn.c:170 [inline]
 hci_conn_del+0xc3d/0x1200 net/bluetooth/hci_conn.c:1308
 hci_disconn_complete_evt+0x5ac/0x890 net/bluetooth/hci_event.c:3470
 hci_event_func net/bluetooth/hci_event.c:7784 [inline]
 hci_event_packet+0x6cd/0xf10 net/bluetooth/hci_event.c:7835
 hci_rx_work+0x3ee/0x1020 net/bluetooth/hci_core.c:4039
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:klist_put lib/klist.c:212 [inline]
RIP: 0010:klist_del lib/klist.c:230 [inline]
RIP: 0010:klist_remove+0x156/0x340 lib/klist.c:249
Code: 4d 89 f5 49 c1 ed 03 43 80 7c 3d 00 00 74 08 4c 89 f7 e8 8d 64 84 f6 4d 8b 26 49 83 e4 fe 49 8d 7c 24 58 48 89 f8 48 c1 e8 03 <42> 80 3c 38 00 74 05 e8 6e 64 84 f6 49 8b 44 24 58 48 89 44 24 08
RSP: 0018:ffffc9000fc87700 EFLAGS: 00010202
RAX: 000000000000000b RBX: ffff888035a90000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000058
RBP: ffffc9000fc877e8 R08: ffffffff90199ae3 R09: 1ffffffff203335c
R10: dffffc0000000000 R11: fffffbfff203335d R12: 0000000000000000
R13: 1ffff1100e64e20c R14: ffff888073271060 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff888125306000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f4691400c30 CR3: 000000007e68e000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
   0:	4d 89 f5             	mov    %r14,%r13
   3:	49 c1 ed 03          	shr    $0x3,%r13
   7:	43 80 7c 3d 00 00    	cmpb   $0x0,0x0(%r13,%r15,1)
   d:	74 08                	je     0x17
   f:	4c 89 f7             	mov    %r14,%rdi
  12:	e8 8d 64 84 f6       	call   0xf68464a4
  17:	4d 8b 26             	mov    (%r14),%r12
  1a:	49 83 e4 fe          	and    $0xfffffffffffffffe,%r12
  1e:	49 8d 7c 24 58       	lea    0x58(%r12),%rdi
  23:	48 89 f8             	mov    %rdi,%rax
  26:	48 c1 e8 03          	shr    $0x3,%rax
* 2a:	42 80 3c 38 00       	cmpb   $0x0,(%rax,%r15,1) <-- trapping instruction
  2f:	74 05                	je     0x36
  31:	e8 6e 64 84 f6       	call   0xf68464a4
  36:	49 8b 44 24 58       	mov    0x58(%r12),%rax
  3b:	48 89 44 24 08       	mov    %rax,0x8(%rsp)


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