Re: [syzbot] [kernel?] WARNING in _cpu_down

[syzbot <syzbot+123e1b70473ce213f3af@syzkaller.appspotmail.com>]

syzbot has found a reproducer for the following issue on:

HEAD commit:    2d1373e4246d Merge tag 'for-7.0-rc4-tag' of git://git.kern..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16b93d52580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=64e78d99d9bf8b4c
dashboard link: https://syzkaller.appspot.com/bug?extid=123e1b70473ce213f3af
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=10d358ba580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=129dc4da580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/2ccba0c603a6/disk-2d1373e4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6aaccd7990b8/vmlinux-2d1373e4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/78e3c8cc74dc/bzImage-2d1373e4.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+123e1b70473ce213f3af@syzkaller.appspotmail.com

smpboot: CPU 1 is now offline
smpboot: Booting Node 0 Processor 1 APIC 0x1
------------[ cut here ]------------
DEAD callback error for CPU1
WARNING: kernel/cpu.c:1463 at _cpu_down+0x759/0x1020 kernel/cpu.c:1463, CPU#0: syz.0.17/6077
Modules linked in:
CPU: 0 UID: 0 PID: 6077 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:_cpu_down+0x75c/0x1020 kernel/cpu.c:1463
Code: 5e 7a f6 89 ee bf 91 00 00 00 e8 df 58 7a f6 81 fd 91 00 00 00 0f 84 6b 02 00 00 e8 1e 5e 7a f6 48 8d 3d f7 f4 4e 05 44 89 ee <67> 48 0f b9 3a e9 3a fa ff ff 45 31 ff e9 32 fa ff ff e8 fd 5d 7a
RSP: 0000:ffffc90003007aa8 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffff8880b85242e0 RCX: ffffffff8b8dba31
RDX: ffff888032059e80 RSI: 0000000000000001 RDI: ffffffff90dcaf40
RBP: 0000000000000092 R08: 0000000000000005 R09: 0000000000000091
R10: 0000000000000092 R11: 0000000000000001 R12: 00000000000000ed
R13: 0000000000000001 R14: 0000000000000001 R15: 00000000fffffff5
FS:  00007f99429dd6c0(0000) GS:ffff88812434a000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fff5c7ffd88 CR3: 00000000747b2000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 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:4196 [inline]
 device_offline+0x2a7/0x3c0 drivers/base/core.c:4180
 online_store+0xd1/0x180 drivers/base/core.c:2809
 dev_attr_store+0x58/0x80 drivers/base/core.c:2437
 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:142
 kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:352
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x6ac/0x1070 fs/read_write.c:688
 ksys_write+0x12a/0x250 fs/read_write.c:740
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f994339c799
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:00007f99429dd028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f9943616090 RCX: 00007f994339c799
RDX: 000000000000000b RSI: 00002000000002c0 RDI: 0000000000000003
RBP: 00007f9943432c99 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9943616128 R14: 00007f9943616090 R15: 00007ffc2a4e69a8
 </TASK>
----------------
Code disassembly (best guess):
   0:	5e                   	pop    %rsi
   1:	7a f6                	jp     0xfffffff9
   3:	89 ee                	mov    %ebp,%esi
   5:	bf 91 00 00 00       	mov    $0x91,%edi
   a:	e8 df 58 7a f6       	call   0xf67a58ee
   f:	81 fd 91 00 00 00    	cmp    $0x91,%ebp
  15:	0f 84 6b 02 00 00    	je     0x286
  1b:	e8 1e 5e 7a f6       	call   0xf67a5e3e
  20:	48 8d 3d f7 f4 4e 05 	lea    0x54ef4f7(%rip),%rdi        # 0x54ef51e
  27:	44 89 ee             	mov    %r13d,%esi
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	e9 3a fa ff ff       	jmp    0xfffffa6e
  34:	45 31 ff             	xor    %r15d,%r15d
  37:	e9 32 fa ff ff       	jmp    0xfffffa6e
  3c:	e8                   	.byte 0xe8
  3d:	fd                   	std
  3e:	5d                   	pop    %rbp
  3f:	7a                   	.byte 0x7a


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