[syzbot] [kernel?] general protection fault in timers_dead_cpu

Hello,

syzbot found the following issue on:

HEAD commit:    db2ddb871435 Linux 7.2-rc7
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14ec2149580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c44651ea7dd2f307
dashboard link: https://syzkaller.appspot.com/bug?extid=74de56995244fe32ffe2
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12ec2149580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16d962c6580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-db2ddb87.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/698def9fcf7a/vmlinux-db2ddb87.xz
kernel image: https://storage.googleapis.com/syzbot-assets/fd8b6091a563/bzImage-db2ddb87.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email protected]

smpboot: CPU 1 is now offline
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 2 UID: 0 PID: 6237 Comm: syz.2.92 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:__hlist_del include/linux/list.h:1029 [inline]
RIP: 0010:detach_timer kernel/time/timer.c:891 [inline]
RIP: 0010:migrate_timer_list kernel/time/timer.c:2493 [inline]
RIP: 0010:timers_dead_cpu+0x326/0x860 kernel/time/timer.c:2541
Code: 0f 85 0c 04 00 00 48 8d 7b 08 48 8b 2b 48 89 f8 48 c1 e8 03 42 80 3c 38 00 0f 85 df 03 00 00 48 8b 43 08 48 89 c2 48 c1 ea 03 <42> 80 3c 3a 00 0f 85 b4 03 00 00 48 89 28 48 89 04 24 48 85 ed 74
RSP: 0018:ffffc900040078c0 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffff88806a523440 RCX: ffffffff81f5d5d8
RDX: 0000000000000000 RSI: ffffffff81f5d420 RDI: ffff88806a523448
RBP: dead000000000122 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffff88806a5258d0
R13: ffffed100d4a4b1a R14: ffff88806a6251c0 R15: dffffc0000000000
FS:  00007f01d4dfe6c0(0000) GS:ffff8880d5fec000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f9c1ca70000 CR3: 000000003de42000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 cpuhp_invoke_callback+0x3b4/0x9a0 kernel/cpu.c:194
 __cpuhp_invoke_callback_range+0x158/0x1d0 kernel/cpu.c:972
 cpuhp_invoke_callback_range kernel/cpu.c:996 [inline]
 cpuhp_down_callbacks kernel/cpu.c:1386 [inline]
 _cpu_down+0x523/0x1020 kernel/cpu.c:1457
 cpu_down_maps_locked kernel/cpu.c:1483 [inline]
 cpu_down kernel/cpu.c:1491 [inline]
 cpu_device_down+0x82/0xc0 kernel/cpu.c:1508
 device_offline drivers/base/core.c:4279 [inline]
 device_offline+0x2f4/0x400 drivers/base/core.c:4263
 online_store+0xd1/0x180 drivers/base/core.c:2879
 dev_attr_store+0x58/0x80 drivers/base/core.c:2505
 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
 kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x6ac/0x1050 fs/read_write.c:687
 ksys_write+0x12a/0x250 fs/read_write.c:739
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f01d579e0d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f01d4dfe028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f01d5a25fa0 RCX: 00007f01d579e0d9
RDX: 0000000000000002 RSI: 0000200000000180 RDI: 0000000000000003
RBP: 00007f01d5835024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f01d5a26038 R14: 00007f01d5a25fa0 R15: 00007ffe4c5cd718
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:__hlist_del include/linux/list.h:1029 [inline]
RIP: 0010:detach_timer kernel/time/timer.c:891 [inline]
RIP: 0010:migrate_timer_list kernel/time/timer.c:2493 [inline]
RIP: 0010:timers_dead_cpu+0x326/0x860 kernel/time/timer.c:2541
Code: 0f 85 0c 04 00 00 48 8d 7b 08 48 8b 2b 48 89 f8 48 c1 e8 03 42 80 3c 38 00 0f 85 df 03 00 00 48 8b 43 08 48 89 c2 48 c1 ea 03 <42> 80 3c 3a 00 0f 85 b4 03 00 00 48 89 28 48 89 04 24 48 85 ed 74
RSP: 0018:ffffc900040078c0 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffff88806a523440 RCX: ffffffff81f5d5d8
RDX: 0000000000000000 RSI: ffffffff81f5d420 RDI: ffff88806a523448
RBP: dead000000000122 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffff88806a5258d0
R13: ffffed100d4a4b1a R14: ffff88806a6251c0 R15: dffffc0000000000
FS:  00007f01d4dfe6c0(0000) GS:ffff8880d5fec000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f9c1ca70000 CR3: 000000003de42000 CR4: 0000000000352ef0
----------------
Code disassembly (best guess):
   0:	0f 85 0c 04 00 00    	jne    0x412
   6:	48 8d 7b 08          	lea    0x8(%rbx),%rdi
   a:	48 8b 2b             	mov    (%rbx),%rbp
   d:	48 89 f8             	mov    %rdi,%rax
  10:	48 c1 e8 03          	shr    $0x3,%rax
  14:	42 80 3c 38 00       	cmpb   $0x0,(%rax,%r15,1)
  19:	0f 85 df 03 00 00    	jne    0x3fe
  1f:	48 8b 43 08          	mov    0x8(%rbx),%rax
  23:	48 89 c2             	mov    %rax,%rdx
  26:	48 c1 ea 03          	shr    $0x3,%rdx
* 2a:	42 80 3c 3a 00       	cmpb   $0x0,(%rdx,%r15,1) <-- trapping instruction
  2f:	0f 85 b4 03 00 00    	jne    0x3e9
  35:	48 89 28             	mov    %rbp,(%rax)
  38:	48 89 04 24          	mov    %rax,(%rsp)
  3c:	48 85 ed             	test   %rbp,%rbp
  3f:	74                   	.byte 0x74


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