[syzbot] [kernel?] general protection fault in detach_timer (2)

[syzbot] [kernel?] general protection fault in detach_timer (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    8bf22c33e7a1 Merge tag 'net-7.0-rc1' of git://git.kernel.o..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1483b6aa580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=abe4fa590468dbfb
dashboard link: https://syzkaller.appspot.com/bug?extid=1a48e52497e1769b08de
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/28e2c9318a17/disk-8bf22c33.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1d96d4ab04ff/vmlinux-8bf22c33.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1c4db52b5202/bzImage-8bf22c33.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1a48e52497e1769b08de@syzkaller.appspotmail.com

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: 16 Comm: ktimers/0 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:__hlist_del include/linux/list.h:994 [inline]
RIP: 0010:detach_timer+0x120/0x300 kernel/time/timer.c:891
Code: c1 e8 03 80 3c 28 00 74 08 4c 89 e7 e8 79 c1 79 00 4d 89 3c 24 4d 85 ff 74 46 e8 bb b3 13 00 49 83 c7 08 4c 89 f8 48 c1 e8 03 <80> 3c 28 00 74 08 4c 89 ff e8 52 c1 79 00 4d 89 27 80 7c 24 04 00
RSP: 0018:ffffc90000157af8 EFLAGS: 00010802
RAX: 1bd5a00000000025 RBX: 1ffff1100bd1b3e7 RCX: ffff88801caa8000
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000100
RBP: dffffc0000000000 R08: 0000000000000000 R09: 0000000000000100
R10: dffffc0000000000 R11: fffffbfff1ed4477 R12: ffffc90000157c00
R13: ffff88805e8d9f40 R14: 1ffff1100bd1b3e8 R15: dead00000000012a
FS:  0000000000000000(0000) GS:ffff888126342000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007eff3f4a9d40 CR3: 0000000035532000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 expire_timers kernel/time/timer.c:1782 [inline]
 __run_timers kernel/time/timer.c:2373 [inline]
 __run_timer_base+0x624/0x9f0 kernel/time/timer.c:2385
 run_timer_base kernel/time/timer.c:2394 [inline]
 run_timer_softirq+0xb7/0x170 kernel/time/timer.c:2404
 handle_softirqs+0x1de/0x6f0 kernel/softirq.c:622
 __do_softirq kernel/softirq.c:656 [inline]
 run_ktimerd+0x69/0x100 kernel/softirq.c:1138
 smpboot_thread_fn+0x541/0xa50 kernel/smpboot.c:160
 kthread+0x388/0x470 kernel/kthread.c:467
 ret_from_fork+0x51e/0xb90 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:__hlist_del include/linux/list.h:994 [inline]
RIP: 0010:detach_timer+0x120/0x300 kernel/time/timer.c:891
Code: c1 e8 03 80 3c 28 00 74 08 4c 89 e7 e8 79 c1 79 00 4d 89 3c 24 4d 85 ff 74 46 e8 bb b3 13 00 49 83 c7 08 4c 89 f8 48 c1 e8 03 <80> 3c 28 00 74 08 4c 89 ff e8 52 c1 79 00 4d 89 27 80 7c 24 04 00
RSP: 0018:ffffc90000157af8 EFLAGS: 00010802
RAX: 1bd5a00000000025 RBX: 1ffff1100bd1b3e7 RCX: ffff88801caa8000
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000100
RBP: dffffc0000000000 R08: 0000000000000000 R09: 0000000000000100
R10: dffffc0000000000 R11: fffffbfff1ed4477 R12: ffffc90000157c00
R13: ffff88805e8d9f40 R14: 1ffff1100bd1b3e8 R15: dead00000000012a
FS:  0000000000000000(0000) GS:ffff888126342000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007eff3f4a9d40 CR3: 0000000035532000 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 79 c1 79 00       	call   0x79c18a
  11:	4d 89 3c 24          	mov    %r15,(%r12)
  15:	4d 85 ff             	test   %r15,%r15
  18:	74 46                	je     0x60
  1a:	e8 bb b3 13 00       	call   0x13b3da
  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 52 c1 79 00       	call   0x79c18a
  38:	4d 89 27             	mov    %r12,(%r15)
  3b:	80 7c 24 04 00       	cmpb   $0x0,0x4(%rsp)


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