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BUG: KASAN: use-after-free in __write_once_size include/linux/compiler.h:295 [inline]
BUG: KASAN: use-after-free in __hlist_del include/linux/list.h:789 [inline]
BUG: KASAN: use-after-free in detach_timer kernel/time/timer.c:824 [inline]
BUG: KASAN: use-after-free in detach_if_pending+0x12d/0x330 kernel/time/timer.c:841
Write of size 8 at addr ffff8881d0ed71c0 by task syz.0.3232/10321

CPU: 1 PID: 10321 Comm: syz.0.3232 Tainted: G        W         5.4.292-syzkaller-00021-gcd8e74fa0fa3 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
 __dump_stack+0x1e/0x20 lib/dump_stack.c:77
 dump_stack+0x15b/0x1b8 lib/dump_stack.c:118
 print_address_description+0x8d/0x4c0 mm/kasan/report.c:384
 __kasan_report+0xef/0x120 mm/kasan/report.c:516
 kasan_report+0x30/0x60 mm/kasan/common.c:653
 __asan_report_store8_noabort+0x17/0x20 mm/kasan/generic_report.c:137
 __write_once_size include/linux/compiler.h:295 [inline]
 __hlist_del include/linux/list.h:789 [inline]
 detach_timer kernel/time/timer.c:824 [inline]
 detach_if_pending+0x12d/0x330 kernel/time/timer.c:841
 try_to_del_timer_sync kernel/time/timer.c:1267 [inline]
 del_timer_sync+0x136/0x1a0 kernel/time/timer.c:1410
 tun_flow_uninit+0x2f/0x2b0 drivers/net/tun.c:1452
 tun_free_netdev+0x7a/0x1b0 drivers/net/tun.c:2404
 netdev_run_todo+0xa45/0xc70 net/core/dev.c:9477
 rtnl_unlock+0xe/0x10 net/core/rtnetlink.c:112
 tun_detach drivers/net/tun.c:766 [inline]
 tun_chr_close+0xc4/0x140 drivers/net/tun.c:3563
 __fput+0x2a3/0x730 fs/file_table.c:281
 ____fput+0x15/0x20 fs/file_table.c:314
 task_work_run+0x146/0x170 kernel/task_work.c:113
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0xa43/0x2660 kernel/exit.c:861
 do_group_exit+0x13e/0x300 kernel/exit.c:984
 get_signal+0xdee/0x13d0 kernel/signal.c:2738
 do_signal+0xad/0xda0 arch/x86/kernel/signal.c:809
 exit_to_usermode_loop+0xc4/0x1b0 arch/x86/entry/common.c:159
 prepare_exit_to_usermode+0x18e/0x1f0 arch/x86/entry/common.c:194
 syscall_return_slowpath arch/x86/entry/common.c:274 [inline]
 do_syscall_64+0x13e/0x170 arch/x86/entry/common.c:300
 entry_SYSCALL_64_after_hwframe+0x5c/0xc1
RIP: 0033:0x7fde1c984969
Code: Bad RIP value.
RSP: 002b:00007fde1afab038 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: fffffffffffffff4 RBX: 00007fde1cbac160 RCX: 00007fde1c984969
RDX: 0000000000000050 RSI: 0000200000000600 RDI: 0000000000000000
RBP: 00007fde1ca06ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000001 R14: 00007fde1cbac160 R15: 00007fff37fd1fc8

The buggy address belongs to the page:
page:ffffea000743b5c0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0x8000000000000000()
raw: 8000000000000000 ffffea000743b588 ffffea0007954908 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x102dc2(GFP_HIGHUSER|__GFP_NOWARN|__GFP_ZERO)
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook mm/page_alloc.c:2165 [inline]
 prep_new_page+0x35e/0x370 mm/page_alloc.c:2171
 get_page_from_freelist+0x1296/0x1310 mm/page_alloc.c:3794
 __alloc_pages_nodemask+0x202/0x4b0 mm/page_alloc.c:4894
 __alloc_pages include/linux/gfp.h:503 [inline]
 __alloc_pages_node include/linux/gfp.h:516 [inline]
 alloc_pages_node include/linux/gfp.h:530 [inline]
 __vmalloc_area_node mm/vmalloc.c:-1 [inline]
 __vmalloc_node_range+0x36a/0x6e0 mm/vmalloc.c:2499
 vmalloc_user+0x73/0x80 mm/vmalloc.c:2629
 kcov_mmap+0x2b/0x120 kernel/kcov.c:450
 call_mmap include/linux/fs.h:1996 [inline]
 mmap_region+0x101b/0x15a0 mm/mmap.c:1812
 do_mmap+0x826/0xd90 mm/mmap.c:1581
 do_mmap_pgoff include/linux/mm.h:2480 [inline]
 vm_mmap_pgoff+0x195/0x230 mm/util.c:528
 ksys_mmap_pgoff+0x16f/0x1e0 mm/mmap.c:1631
 __do_sys_mmap arch/x86/kernel/sys_x86_64.c:97 [inline]
 __se_sys_mmap arch/x86/kernel/sys_x86_64.c:88 [inline]
 __x64_sys_mmap+0xfa/0x110 arch/x86/kernel/sys_x86_64.c:88
 do_syscall_64+0xcf/0x170 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x5c/0xc1
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1176 [inline]
 free_pcp_prepare mm/page_alloc.c:1233 [inline]
 free_unref_page_prepare+0x2a9/0x3a0 mm/page_alloc.c:3085
 free_unref_page mm/page_alloc.c:3134 [inline]
 free_the_page mm/page_alloc.c:4954 [inline]
 __free_pages+0xaa/0x110 mm/page_alloc.c:4962
 __vunmap+0x76a/0x8a0 mm/vmalloc.c:2260
 __vfree mm/vmalloc.c:2308 [inline]
 vfree+0x61/0x90 mm/vmalloc.c:2338
 kcov_mmap+0x8c/0x120 kernel/kcov.c:474
 call_mmap include/linux/fs.h:1996 [inline]
 mmap_region+0x101b/0x15a0 mm/mmap.c:1812
 do_mmap+0x826/0xd90 mm/mmap.c:1581
 do_mmap_pgoff include/linux/mm.h:2480 [inline]
 vm_mmap_pgoff+0x195/0x230 mm/util.c:528
 ksys_mmap_pgoff+0x16f/0x1e0 mm/mmap.c:1631
 __do_sys_mmap arch/x86/kernel/sys_x86_64.c:97 [inline]
 __se_sys_mmap arch/x86/kernel/sys_x86_64.c:88 [inline]
 __x64_sys_mmap+0xfa/0x110 arch/x86/kernel/sys_x86_64.c:88
 do_syscall_64+0xcf/0x170 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x5c/0xc1

Memory state around the buggy address:
 ffff8881d0ed7080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881d0ed7100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8881d0ed7180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                           ^
 ffff8881d0ed7200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881d0ed7280: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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