[v6.6] general protection fault in __cpuhp_state_remove_instance

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c5596480c50e Linux 6.6.145
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1059249e580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f0bc3d90c30838b5
dashboard link: https://syzkaller.appspot.com/bug?extid=c81c88952a7b76f7ad15
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/eb5cda0a8020/disk-c5596480.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ca05ff2fc502/vmlinux-c5596480.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6daf3255b985/bzImage-c5596480.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c81c88...@syzkaller.appspotmail.com

raid456_cpu_up_prepare: failed memory allocation for cpu0
general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 1 PID: 11662 Comm: syz.0.1914 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:__hlist_del include/linux/list.h:980 [inline]
RIP: 0010:hlist_del include/linux/list.h:994 [inline]
RIP: 0010:__cpuhp_state_remove_instance+0x217/0x2e0 kernel/cpu.c:2610
Code: 8b 3b 48 89 1c 24 48 83 c3 08 49 89 de 49 c1 ee 03 43 80 3c 2e 00 74 08 48 89 df e8 b3 4f 8e 00 4c 8b 23 4c 89 e0 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 e7 e8 3a 50 8e 00 4d 89 3c 24 4d 85 ff
RSP: 0018:ffffc9000344f790 EFLAGS: 00010246

RAX: 0000000000000000 RBX: ffff8880245e8430 RCX: 0000000000080000
RDX: ffffc9000b9a1000 RSI: 000000000007ffff RDI: 0000000000080000
RBP: 1ffff110048bd085 R08: ffffffff8e8c7caf R09: 1ffffffff1d18f95
R10: dffffc0000000000 R11: fffffbfff1d18f96 R12: 0000000000000000
R13: dffffc0000000000 R14: 1ffff110048bd086 R15: 0000000000000000
FS: 00007fd464d176c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fca2cca3bb8 CR3: 000000002bc95000 CR4: 00000000003506e0
Call Trace:
<TASK>
cpuhp_state_remove_instance include/linux/cpuhotplug.h:499 [inline]
raid5_free_percpu drivers/md/raid5.c:7423 [inline]
free_conf+0x294/0x4b0 drivers/md/raid5.c:7436
setup_conf+0x16c4/0x2a30 drivers/md/raid5.c:7765
raid5_run+0x8ac/0x2a00 drivers/md/raid5.c:7943
md_run+0x10b3/0x2210 drivers/md/md.c:6023
do_md_run+0x34/0x410 drivers/md/md.c:6155
md_ioctl+0x20f4/0x24d0 drivers/md/md.c:7825
blkdev_ioctl+0x5b2/0x730 block/ioctl.c:639
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:871 [inline]
__se_sys_ioctl+0xfd/0x170 fs/ioctl.c:857
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fd463d9de99
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:00007fd464d17028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fd464025fa0 RCX: 00007fd463d9de99
RDX: 0000000000000000 RSI: 00000000400c0930 RDI: 000000000000000c
RBP: 00007fd463e33eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd464026038 R14: 00007fd464025fa0 R15: 00007ffe511451e8
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:__hlist_del include/linux/list.h:980 [inline]
RIP: 0010:hlist_del include/linux/list.h:994 [inline]
RIP: 0010:__cpuhp_state_remove_instance+0x217/0x2e0 kernel/cpu.c:2610
Code: 8b 3b 48 89 1c 24 48 83 c3 08 49 89 de 49 c1 ee 03 43 80 3c 2e 00 74 08 48 89 df e8 b3 4f 8e 00 4c 8b 23 4c 89 e0 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 e7 e8 3a 50 8e 00 4d 89 3c 24 4d 85 ff
RSP: 0018:ffffc9000344f790 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8880245e8430 RCX: 0000000000080000
RDX: ffffc9000b9a1000 RSI: 000000000007ffff RDI: 0000000000080000
RBP: 1ffff110048bd085 R08: ffffffff8e8c7caf R09: 1ffffffff1d18f95
R10: dffffc0000000000 R11: fffffbfff1d18f96 R12: 0000000000000000
R13: dffffc0000000000 R14: 1ffff110048bd086 R15: 0000000000000000
FS: 00007fd464d176c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f3369f6f000 CR3: 000000002bc95000 CR4: 00000000003506f0
----------------
Code disassembly (best guess):
0: 8b 3b mov (%rbx),%edi
2: 48 89 1c 24 mov %rbx,(%rsp)
6: 48 83 c3 08 add $0x8,%rbx
a: 49 89 de mov %rbx,%r14
d: 49 c1 ee 03 shr $0x3,%r14
11: 43 80 3c 2e 00 cmpb $0x0,(%r14,%r13,1)
16: 74 08 je 0x20
18: 48 89 df mov %rbx,%rdi
1b: e8 b3 4f 8e 00 call 0x8e4fd3
20: 4c 8b 23 mov (%rbx),%r12
23: 4c 89 e0 mov %r12,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 80 3c 28 00 cmpb $0x0,(%rax,%r13,1) <-- trapping instruction
2f: 74 08 je 0x39
31: 4c 89 e7 mov %r12,%rdi
34: e8 3a 50 8e 00 call 0x8e5073
39: 4d 89 3c 24 mov %r15,(%r12)
3d: 4d 85 ff test %r15,%r15


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