Re: [syzbot] [edac?] general protection fault in detach_timer (3)

[syzbot <syzbot+edc6b57cbed1fb72d0f9@syzkaller.appspotmail.com>]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
general protection fault in detach_timer

Oops: general protection fault, probably for non-canonical address 0xfbd59c0000000025: 0000 [#1] SMP KASAN PTI
KASAN: maybe wild-memory-access in range [0xdead000000000128-0xdead00000000012f]
CPU: 0 UID: 0 PID: 6706 Comm: syz.0.35 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:__hlist_del include/linux/list.h:1031 [inline]
RIP: 0010:detach_timer+0x120/0x2d0 kernel/time/timer.c:891
Code: c1 e8 03 80 3c 28 00 74 08 4c 89 e7 e8 c9 48 7d 00 4d 89 3c 24 4d 85 ff 74 46 e8 4b d1 13 00 49 83 c7 08 4c 89 f8 48 c1 e8 03 <80> 3c 28 00 74 08 4c 89 ff e8 a2 48 7d 00 4d 89 27 80 7c 24 04 00
RSP: 0018:ffffc9000492fae8 EFLAGS: 00010802
RAX: 1bd5a00000000025 RBX: 1ffff110170e4694 RCX: ffff888031879f00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: dffffc0000000000 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff1f5e987 R12: ffff8880b86258f0
R13: ffff8880b87234a8 R14: 1ffff110170e4695 R15: dead00000000012a
FS:  00007f01d31bd6c0(0000) GS:ffff888125c46000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f01d3bcb7c0 CR3: 0000000032b9e000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 detach_if_pending kernel/time/timer.c:910 [inline]
 __try_to_del_timer_sync kernel/time/timer.c:1462 [inline]
 __timer_delete_sync+0x4fb/0x600 kernel/time/timer.c:1621
 mce_timer_delete_all arch/x86/kernel/cpu/mce/core.c:1817 [inline]
 set_ignore_ce+0x1c2/0x2a0 arch/x86/kernel/cpu/mce/core.c:2562
 kernfs_fop_write_iter+0x3a5/0x540 fs/kernfs/file.c:345
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x61e/0xbb0 fs/read_write.c:687
 ksys_write+0x156/0x270 fs/read_write.c:739
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f01d3b7e0d9
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:00007f01d31bd028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f01d3e06090 RCX: 00007f01d3b7e0d9
RDX: 0000000000000002 RSI: 00002000000001a0 RDI: 0000000000000003
RBP: 00007f01d3c15024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f01d3e06128 R14: 00007f01d3e06090 R15: 00007ffc28e9bd68
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:__hlist_del include/linux/list.h:1031 [inline]
RIP: 0010:detach_timer+0x120/0x2d0 kernel/time/timer.c:891
Code: c1 e8 03 80 3c 28 00 74 08 4c 89 e7 e8 c9 48 7d 00 4d 89 3c 24 4d 85 ff 74 46 e8 4b d1 13 00 49 83 c7 08 4c 89 f8 48 c1 e8 03 <80> 3c 28 00 74 08 4c 89 ff e8 a2 48 7d 00 4d 89 27 80 7c 24 04 00
RSP: 0018:ffffc9000492fae8 EFLAGS: 00010802
RAX: 1bd5a00000000025 RBX: 1ffff110170e4694 RCX: ffff888031879f00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: dffffc0000000000 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff1f5e987 R12: ffff8880b86258f0
R13: ffff8880b87234a8 R14: 1ffff110170e4695 R15: dead00000000012a
FS:  00007f01d31bd6c0(0000) GS:ffff888125c46000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f01d3bcb7c0 CR3: 0000000032b9e000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
   0:	c1 e8 03             	shr    $0x3,%eax
   3:	80 3c 28 00          	cmpb   $0x0,(%rax,%rbp,1)
   7:	74 08                	je     0x11
   9:	4c 89 e7             	mov    %r12,%rdi
   c:	e8 c9 48 7d 00       	call   0x7d48da
  11:	4d 89 3c 24          	mov    %r15,(%r12)
  15:	4d 85 ff             	test   %r15,%r15
  18:	74 46                	je     0x60
  1a:	e8 4b d1 13 00       	call   0x13d16a
  1f:	49 83 c7 08          	add    $0x8,%r15
  23:	4c 89 f8             	mov    %r15,%rax
  26:	48 c1 e8 03          	shr    $0x3,%rax
* 2a:	80 3c 28 00          	cmpb   $0x0,(%rax,%rbp,1) <-- trapping instruction
  2e:	74 08                	je     0x38
  30:	4c 89 ff             	mov    %r15,%rdi
  33:	e8 a2 48 7d 00       	call   0x7d48da
  38:	4d 89 27             	mov    %r12,(%r15)
  3b:	80 7c 24 04 00       	cmpb   $0x0,0x4(%rsp)


Tested on:

commit:         cfeb0849 timers: Abort CPU hotplug on corrupted timer ..
git tree:       https://github.com/yutao-intel/linux.git fix-edac
console output: https://syzkaller.appspot.com/x/log.txt?x=148bec79580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=158601bb8cb292dd
dashboard link: https://syzkaller.appspot.com/bug?extid=edc6b57cbed1fb72d0f9
compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

Note: no patches were applied.