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BUG: KASAN: use-after-free in __hlist_del include/linux/list.h:764 [inline]
BUG: KASAN: use-after-free in detach_timer kernel/time/timer.c:824 [inline]
BUG: KASAN: use-after-free in detach_if_pending kernel/time/timer.c:841 [inline]
BUG: KASAN: use-after-free in try_to_del_timer_sync+0x2b1/0x460 kernel/time/timer.c:1238
Write of size 8 at addr ffff8881e58ab1c8 by task syz-executor.0/9915

CPU: 0 PID: 9915 Comm: syz-executor.0 Not tainted 5.4.113-syzkaller-00288-ga5631d493c29 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1d8/0x24e lib/dump_stack.c:118
 print_address_description+0x9b/0x650 mm/kasan/report.c:384
 __kasan_report+0x182/0x260 mm/kasan/report.c:516
 kasan_report+0x30/0x60 mm/kasan/common.c:641
 __hlist_del include/linux/list.h:764 [inline]
 detach_timer kernel/time/timer.c:824 [inline]
 detach_if_pending kernel/time/timer.c:841 [inline]
 try_to_del_timer_sync+0x2b1/0x460 kernel/time/timer.c:1238
 del_timer_sync+0x78/0xe0 kernel/time/timer.c:1377
 tun_flow_uninit drivers/net/tun.c:1382 [inline]
 tun_free_netdev+0x99/0x3b0 drivers/net/tun.c:2323
 netdev_run_todo+0xb31/0xda0 net/core/dev.c:9408
 tun_detach drivers/net/tun.c:751 [inline]
 tun_chr_close+0xc0/0xd0 drivers/net/tun.c:3517
 __fput+0x27d/0x6c0 fs/file_table.c:281
 task_work_run+0x186/0x1b0 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop arch/x86/entry/common.c:163 [inline]
 prepare_exit_to_usermode+0x2b0/0x310 arch/x86/entry/common.c:194
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x41926b
Code: 0f 05 48 3d 00 f0 ff ff 77 45 c3 0f 1f 40 00 48 83 ec 18 89 7c 24 0c e8 63 fc ff ff 8b 7c 24 0c 41 89 c0 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 35 44 89 c7 89 44 24 0c e8 a1 fc ff ff 8b 44
RSP: 002b:00007ffd50c5a6d0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000004 RCX: 000000000041926b
RDX: 00000000005701c0 RSI: 0000000008907ca6 RDI: 0000000000000003
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000001b31a21dac
R10: 00007ffd50c5a7c0 R11: 0000000000000293 R12: 0000000000034ffd
R13: 00000000000003e8 R14: 000000000056bf60 R15: 0000000000034fe3

The buggy address belongs to the page:
page:ffffea0007962ac0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0x8000000000000000()
raw: 8000000000000000 ffffea0007b29408 ffffea0007962a88 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8881e58ab080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881e58ab100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8881e58ab180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                              ^
 ffff8881e58ab200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881e58ab280: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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