==================================================================
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 ffff8881dcecb1c0 by task syz.5.1044/4174

CPU: 1 PID: 4174 Comm: syz.5.1044 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: 0033:0x7f3b52bbf969
Code: Bad RIP value.
RSP: 002b:00007f3b511e6038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffef RBX: 00007f3b52de7160 RCX: 00007f3b52bbf969
RDX: 0000200000000200 RSI: 00000000400454ca RDI: 0000000000000003
RBP: 00007f3b52c41ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000001 R14: 00007f3b52de7160 R15: 00007fff9c316a88

Allocated by task 4168:
 save_stack mm/kasan/common.c:70 [inline]
 set_track mm/kasan/common.c:78 [inline]
 __kasan_kmalloc+0x162/0x200 mm/kasan/common.c:529
 kasan_slab_alloc+0x12/0x20 mm/kasan/common.c:537
 slab_post_alloc_hook mm/slab.h:584 [inline]
 slab_alloc_node mm/slub.c:2829 [inline]
 slab_alloc mm/slub.c:2837 [inline]
 __kmalloc_track_caller+0x10d/0x2d0 mm/slub.c:4449
 __kmalloc_reserve net/core/skbuff.c:142 [inline]
 __alloc_skb+0xdc/0x500 net/core/skbuff.c:210
 alloc_skb include/linux/skbuff.h:1080 [inline]
 nlmsg_new include/net/netlink.h:888 [inline]
 inet_netconf_notify_devconf+0x169/0x220 net/ipv4/devinet.c:2121
 __devinet_sysctl_register+0x324/0x390 net/ipv4/devinet.c:2608
 devinet_sysctl_register+0x169/0x1e0 net/ipv4/devinet.c:2642
 inetdev_init+0x28a/0x430 net/ipv4/devinet.c:277
 inetdev_event+0x1f8/0x1030 net/ipv4/devinet.c:1545
 notifier_call_chain kernel/notifier.c:98 [inline]
 __raw_notifier_call_chain kernel/notifier.c:399 [inline]
 raw_notifier_call_chain+0xa0/0x120 kernel/notifier.c:406
 call_netdevice_notifiers_info net/core/dev.c:1670 [inline]
 call_netdevice_notifiers_extack net/core/dev.c:1682 [inline]
 call_netdevice_notifiers net/core/dev.c:1696 [inline]
 register_netdevice+0xeb9/0x12a0 net/core/dev.c:9240
 __ip_tunnel_create+0x2bf/0x380 net/ipv4/ip_tunnel.c:267
 ip_tunnel_init_net+0x277/0x710 net/ipv4/ip_tunnel.c:1076
 ipgre_init_net+0x24/0x30 net/ipv4/ip_gre.c:1032
 ops_init+0x1ba/0x4a0 net/core/net_namespace.c:141
 setup_net+0x20c/0x9b0 net/core/net_namespace.c:348
 copy_net_ns+0x314/0x520 net/core/net_namespace.c:489
 create_new_namespaces+0x49c/0x590 kernel/nsproxy.c:103
 copy_namespaces+0x17e/0x1c0 kernel/nsproxy.c:161
 copy_process+0x1194/0x2cf0 kernel/fork.c:2055
 _do_fork+0x190/0x860 kernel/fork.c:2399
 __do_sys_clone kernel/fork.c:2557 [inline]
 __se_sys_clone kernel/fork.c:2538 [inline]
 __x64_sys_clone+0x12e/0x160 kernel/fork.c:2538
 do_syscall_64+0xcf/0x170 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x5c/0xc1

Freed by task 4168:
 save_stack mm/kasan/common.c:70 [inline]
 set_track mm/kasan/common.c:78 [inline]
 kasan_set_free_info mm/kasan/common.c:345 [inline]
 __kasan_slab_free+0x1c3/0x280 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
 skb_free_head net/core/skbuff.c:601 [inline]
 skb_release_data+0x4ea/0x610 net/core/skbuff.c:621
 skb_release_all net/core/skbuff.c:675 [inline]
 __kfree_skb net/core/skbuff.c:689 [inline]
 consume_skb+0xad/0x240 net/core/skbuff.c:849
 netlink_broadcast_filtered+0x1198/0x1290 net/netlink/af_netlink.c:1516
 netlink_broadcast net/netlink/af_netlink.c:1538 [inline]
 nlmsg_multicast include/net/netlink.h:968 [inline]
 nlmsg_notify+0xed/0x1b0 net/netlink/af_netlink.c:2510
 rtnl_notify+0x9a/0xc0 net/core/rtnetlink.c:737
 inet_netconf_notify_devconf+0x1c2/0x220 net/ipv4/devinet.c:2133
 __devinet_sysctl_register+0x324/0x390 net/ipv4/devinet.c:2608
 devinet_sysctl_register+0x169/0x1e0 net/ipv4/devinet.c:2642
 inetdev_init+0x28a/0x430 net/ipv4/devinet.c:277
 inetdev_event+0x1f8/0x1030 net/ipv4/devinet.c:1545
 notifier_call_chain kernel/notifier.c:98 [inline]
 __raw_notifier_call_chain kernel/notifier.c:399 [inline]
 raw_notifier_call_chain+0xa0/0x120 kernel/notifier.c:406
 call_netdevice_notifiers_info net/core/dev.c:1670 [inline]
 call_netdevice_notifiers_extack net/core/dev.c:1682 [inline]
 call_netdevice_notifiers net/core/dev.c:1696 [inline]
 register_netdevice+0xeb9/0x12a0 net/core/dev.c:9240
 __ip_tunnel_create+0x2bf/0x380 net/ipv4/ip_tunnel.c:267
 ip_tunnel_init_net+0x277/0x710 net/ipv4/ip_tunnel.c:1076
 ipgre_init_net+0x24/0x30 net/ipv4/ip_gre.c:1032
 ops_init+0x1ba/0x4a0 net/core/net_namespace.c:141
 setup_net+0x20c/0x9b0 net/core/net_namespace.c:348
 copy_net_ns+0x314/0x520 net/core/net_namespace.c:489
 create_new_namespaces+0x49c/0x590 kernel/nsproxy.c:103
 copy_namespaces+0x17e/0x1c0 kernel/nsproxy.c:161
 copy_process+0x1194/0x2cf0 kernel/fork.c:2055
 _do_fork+0x190/0x860 kernel/fork.c:2399
 __do_sys_clone kernel/fork.c:2557 [inline]
 __se_sys_clone kernel/fork.c:2538 [inline]
 __x64_sys_clone+0x12e/0x160 kernel/fork.c:2538
 do_syscall_64+0xcf/0x170 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x5c/0xc1

The buggy address belongs to the object at ffff8881dcecb000
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 448 bytes inside of
 512-byte region [ffff8881dcecb000, ffff8881dcecb200)
The buggy address belongs to the page:
page:ffffea000773b200 refcount:1 mapcount:0 mapping:ffff8881f5c02500 index:0x0 compound_mapcount: 0
flags: 0x8000000000010200(slab|head)
raw: 8000000000010200 dead000000000100 dead000000000122 ffff8881f5c02500
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__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_slab_page+0x3c/0x3b0 mm/slub.c:343
 allocate_slab mm/slub.c:1683 [inline]
 new_slab+0x93/0x420 mm/slub.c:1749
 new_slab_objects mm/slub.c:2505 [inline]
 ___slab_alloc+0x29e/0x420 mm/slub.c:2667
 __slab_alloc+0x63/0xa0 mm/slub.c:2707
 slab_alloc_node mm/slub.c:2792 [inline]
 slab_alloc mm/slub.c:2837 [inline]
 __kmalloc_track_caller+0x17c/0x2d0 mm/slub.c:4449
 __kmalloc_reserve net/core/skbuff.c:142 [inline]
 __alloc_skb+0xdc/0x500 net/core/skbuff.c:210
 alloc_skb include/linux/skbuff.h:1080 [inline]
 alloc_uevent_skb+0x85/0x240 lib/kobject_uevent.c:290
 uevent_net_broadcast_tagged lib/kobject_uevent.c:351 [inline]
 kobject_uevent_net_broadcast+0x1a6/0x5a0 lib/kobject_uevent.c:412
 kobject_uevent_env+0x52a/0x6e0 lib/kobject_uevent.c:608
 kobject_uevent+0x1d/0x30 lib/kobject_uevent.c:657
 device_add+0x823/0xc90 drivers/base/core.c:2892
 netdev_register_kobject+0x179/0x320 net/core/net-sysfs.c:1854
 register_netdevice+0xbd4/0x12a0 net/core/dev.c:9209
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+0x8c/0x110 mm/page_alloc.c:4962
 kfree+0x1ca/0x260 mm/slub.c:4068
 kvfree+0x4c/0x50 mm/util.c:625
 netdev_freemem+0x3f/0x60 net/core/dev.c:9583
 netdev_release+0x7f/0xb0 net/core/net-sysfs.c:1743
 device_release+0x70/0x1a0 drivers/base/core.c:1776
 kobject_cleanup lib/kobject.c:716 [inline]
 kobject_release lib/kobject.c:747 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x1fe/0x2c0 lib/kobject.c:764
 put_device+0x1f/0x30 drivers/base/core.c:3010
 free_netdev+0x27e/0x320 net/core/dev.c:9746
 tun_set_iff+0x87c/0xe00 drivers/net/tun.c:2924
 __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

Memory state around the buggy address:
 ffff8881dcecb080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881dcecb100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881dcecb180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                           ^
 ffff8881dcecb200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8881dcecb280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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