syzbot

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refcount_t: underflow; use-after-free.
WARNING: CPU: 1 PID: 29 at lib/refcount.c:28 refcount_warn_saturate+0x11a/0x1d0 lib/refcount.c:28
Modules linked in:
CPU: 1 UID: 0 PID: 29 Comm: ktimers/1 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:refcount_warn_saturate+0x11a/0x1d0 lib/refcount.c:28
Code: 80 2e 3d 8b e8 57 a1 09 fd 90 0f 0b 90 90 eb d7 e8 2b 5c 45 fd c6 05 b7 08 47 0a 01 90 48 c7 c7 e0 2e 3d 8b e8 37 a1 09 fd 90 <0f> 0b 90 90 eb b7 e8 0b 5c 45 fd c6 05 94 08 47 0a 01 90 48 c7 c7
RSP: 0018:ffffc90000a3f888 EFLAGS: 00010246
RAX: 50bb8b3d5a5db200 RBX: 0000000000000003 RCX: ffff88801bea9e00
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000100
RBP: ffffc90000a3f990 R08: 0000000000000000 R09: 0000000000000100
R10: dffffc0000000000 R11: ffffed101712487b R12: 1ffff92000147f18
R13: ffff8880317649b8 R14: ffff888031764820 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff888126ef9000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00002000000008c0 CR3: 0000000035fec000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 call_timer_fn+0x17e/0x5f0 kernel/time/timer.c:1747
 expire_timers kernel/time/timer.c:1798 [inline]
 __run_timers kernel/time/timer.c:2372 [inline]
 __run_timer_base+0x648/0x970 kernel/time/timer.c:2384
 run_timer_base kernel/time/timer.c:2393 [inline]
 run_timer_softirq+0xb7/0x180 kernel/time/timer.c:2403
 handle_softirqs+0x22f/0x710 kernel/softirq.c:622
 __do_softirq kernel/softirq.c:656 [inline]
 run_ktimerd+0xcf/0x190 kernel/softirq.c:1138
 smpboot_thread_fn+0x542/0xa60 kernel/smpboot.c:160
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>