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BUG: KASAN: use-after-free in hlist_add_head include/linux/list.h:814 [inline]
BUG: KASAN: use-after-free in enqueue_timer+0x9e/0x2c0 kernel/time/timer.c:541
Write of size 8 at addr ffff8881e116f1c8 by task syz.4.503/2059

CPU: 1 PID: 2059 Comm: syz.4.503 Not tainted 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
 hlist_add_head include/linux/list.h:814 [inline]
 enqueue_timer+0x9e/0x2c0 kernel/time/timer.c:541
 __internal_add_timer kernel/time/timer.c:554 [inline]
 internal_add_timer+0x208/0x3e0 kernel/time/timer.c:604
 __mod_timer+0x5ab/0x1150 kernel/time/timer.c:1065
 mod_timer+0x1f/0x30 kernel/time/timer.c:1117
 tun_flow_init drivers/net/tun.c:1446 [inline]
 tun_net_init+0x2ba/0x580 drivers/net/tun.c:1055
 register_netdevice+0x1c4/0x12a0 net/core/dev.c:9139
 tun_set_iff+0x812/0xe00 drivers/net/tun.c:2922
 __tun_chr_ioctl+0x771/0x18a0 drivers/net/tun.c:3187
 tun_chr_ioctl+0x2a/0x40 drivers/net/tun.c:3470
 do_vfs_ioctl+0x753/0x13f0 fs/ioctl.c:47
 ksys_ioctl fs/ioctl.c:742 [inline]
 __do_sys_ioctl fs/ioctl.c:749 [inline]
 __se_sys_ioctl fs/ioctl.c:747 [inline]
 __x64_sys_ioctl+0xe1/0x120 fs/ioctl.c:747
 do_syscall_64+0xcf/0x170 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x5c/0xc1
RIP: 0033:0x7f647fa3c969
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f647e0a5038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f647fc63fa0 RCX: 00007f647fa3c969
RDX: 0000200000000080 RSI: 00000000400454ca RDI: 0000000000000005
RBP: 00007f647fabeab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f647fc63fa0 R15: 00007ffdf85f1688

The buggy address belongs to the page:
page:ffffea0007845bc0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0x8000000000000000()
raw: 8000000000000000 ffffea000799be08 ffffea0007845b88 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 2, migratetype Unmovable, gfp_mask 0x102800(GFP_NOWAIT|__GFP_NOWARN|__GFP_HARDWALL)
 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]
 stack_depot_save+0x3a3/0x4c0 lib/stackdepot.c:267
 save_stack mm/kasan/common.c:72 [inline]
 set_track mm/kasan/common.c:78 [inline]
 kasan_set_free_info mm/kasan/common.c:345 [inline]
 __kasan_slab_free+0x223/0x280 mm/kasan/common.c:487
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:496
 slab_free_hook mm/slub.c:1455 [inline]
 slab_free_freelist_hook+0xb7/0x180 mm/slub.c:1494
 slab_free mm/slub.c:3080 [inline]
 kfree+0xbe/0x260 mm/slub.c:4071
 kobject_uevent_env+0x342/0x6e0 lib/kobject_uevent.c:640
 kobject_uevent+0x1d/0x30 lib/kobject_uevent.c:657
 device_del+0xe98/0xfb0 drivers/base/core.c:3098
 netdev_unregister_kobject+0x184/0x250 net/core/net-sysfs.c:1820
 rollback_registered_many+0xc4c/0xf40 net/core/dev.c:8674
 rollback_registered net/core/dev.c:8692 [inline]
 unregister_netdevice_queue+0x2e1/0x450 net/core/dev.c:9786
 unregister_netdevice include/linux/netdevice.h:2732 [inline]
 __tun_detach+0xb40/0x1340 drivers/net/tun.c:747
 tun_detach drivers/net/tun.c:763 [inline]
 tun_chr_close+0x92/0x140 drivers/net/tun.c:3563
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_pages_ok+0x7e4/0x910 mm/page_alloc.c:1438
 free_the_page mm/page_alloc.c:4956 [inline]
 __free_pages mm/page_alloc.c:4962 [inline]
 free_pages+0xf9/0x180 mm/page_alloc.c:4970
 stack_depot_save+0x492/0x4c0 lib/stackdepot.c:300
 save_stack mm/kasan/common.c:72 [inline]
 set_track mm/kasan/common.c:78 [inline]
 kasan_set_free_info mm/kasan/common.c:345 [inline]
 __kasan_slab_free+0x223/0x280 mm/kasan/common.c:487
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:496
 slab_free_hook mm/slub.c:1455 [inline]
 slab_free_freelist_hook+0xb7/0x180 mm/slub.c:1494
 slab_free mm/slub.c:3080 [inline]
 kfree+0xbe/0x260 mm/slub.c:4071
 kobject_uevent_env+0x342/0x6e0 lib/kobject_uevent.c:640
 kobject_uevent+0x1d/0x30 lib/kobject_uevent.c:657
 device_del+0xe98/0xfb0 drivers/base/core.c:3098
 netdev_unregister_kobject+0x184/0x250 net/core/net-sysfs.c:1820
 rollback_registered_many+0xc4c/0xf40 net/core/dev.c:8674
 rollback_registered net/core/dev.c:8692 [inline]
 unregister_netdevice_queue+0x2e1/0x450 net/core/dev.c:9786
 unregister_netdevice include/linux/netdevice.h:2732 [inline]
 __tun_detach+0xb40/0x1340 drivers/net/tun.c:747
 tun_detach drivers/net/tun.c:763 [inline]
 tun_chr_close+0x92/0x140 drivers/net/tun.c:3563
 __fput+0x2a3/0x730 fs/file_table.c:281

Memory state around the buggy address:
 ffff8881e116f080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881e116f100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8881e116f180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                              ^
 ffff8881e116f200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881e116f280: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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