==================================================================
BUG: KASAN: use-after-free in hlist_add_head include/linux/list.h:814 [inline]
BUG: KASAN: use-after-free in enqueue_timer+0xb7/0x300 kernel/time/timer.c:541
Write of size 8 at addr ffff8881eb2cf1c8 by task syz.2.763/3071

CPU: 0 PID: 3071 Comm: syz.2.763 Not tainted 5.4.274-syzkaller-00003-g51e9abf68baf #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1d8/0x241 lib/dump_stack.c:118
 print_address_description+0x8c/0x600 mm/kasan/report.c:384
 __kasan_report+0xf3/0x120 mm/kasan/report.c:516
 kasan_report+0x30/0x60 mm/kasan/common.c:653
 hlist_add_head include/linux/list.h:814 [inline]
 enqueue_timer+0xb7/0x300 kernel/time/timer.c:541
 __internal_add_timer kernel/time/timer.c:554 [inline]
 internal_add_timer+0x240/0x430 kernel/time/timer.c:604
 __mod_timer+0x6f1/0x13e0 kernel/time/timer.c:1065
 tun_flow_init drivers/net/tun.c:1446 [inline]
 tun_net_init+0x287/0x540 drivers/net/tun.c:1055
 register_netdevice+0x1c0/0x12a0 net/core/dev.c:9120
 tun_set_iff+0x7f7/0xdc0 drivers/net/tun.c:2917
 __tun_chr_ioctl+0x8a9/0x1d00 drivers/net/tun.c:3182
 do_vfs_ioctl+0x742/0x1720 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+0xd4/0x110 fs/ioctl.c:747
 do_syscall_64+0xca/0x1c0 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x5c/0xc1
RIP: 0033:0x7f3f86f39b99
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:00007f3f861bb048 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f3f870c7fa0 RCX: 00007f3f86f39b99
RDX: 00000000200000c0 RSI: 00000000400454ca RDI: 0000000000000006
RBP: 00007f3f86fba77e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f3f870c7fa0 R15: 00007ffed7a3ed78

Allocated by task 5:
 save_stack mm/kasan/common.c:70 [inline]
 set_track mm/kasan/common.c:78 [inline]
 __kasan_kmalloc+0x171/0x210 mm/kasan/common.c:529
 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+0x100/0x2b0 mm/slub.c:4449
 __kmalloc_reserve net/core/skbuff.c:142 [inline]
 __alloc_skb+0xb4/0x4d0 net/core/skbuff.c:210
 alloc_skb include/linux/skbuff.h:1080 [inline]
 ndisc_alloc_skb+0xee/0x2c0 net/ipv6/ndisc.c:421
 ndisc_send_ns+0x29d/0x830 net/ipv6/ndisc.c:627
 addrconf_dad_work+0xb91/0x16f0 net/ipv6/addrconf.c:4194
 process_one_work+0x765/0xd20 kernel/workqueue.c:2290
 worker_thread+0xaef/0x1470 kernel/workqueue.c:2436
 kthread+0x2da/0x360 kernel/kthread.c:288
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:354

Freed by task 5:
 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+0x1b5/0x270 mm/kasan/common.c:487
 slab_free_hook mm/slub.c:1455 [inline]
 slab_free_freelist_hook mm/slub.c:1494 [inline]
 slab_free mm/slub.c:3080 [inline]
 kfree+0x123/0x370 mm/slub.c:4071
 skb_release_all net/core/skbuff.c:675 [inline]
 __kfree_skb net/core/skbuff.c:689 [inline]
 kfree_skb+0xb8/0x3c0 net/core/skbuff.c:708
 ip6_mc_input+0x236/0x2a0 net/ipv6/ip6_input.c:550
 NF_HOOK include/linux/netfilter.h:303 [inline]
 ipv6_rcv+0xee/0x280 net/ipv6/ip6_input.c:278
 __netif_receive_skb_one_core net/core/dev.c:4972 [inline]
 __netif_receive_skb+0x1c6/0x530 net/core/dev.c:5086
 process_backlog+0x34f/0x680 net/core/dev.c:5921
 napi_poll net/core/dev.c:6367 [inline]
 net_rx_action+0x53f/0x1160 net/core/dev.c:6435
 __do_softirq+0x23b/0x6b7 kernel/softirq.c:292

The buggy address belongs to the object at ffff8881eb2cf000
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 456 bytes inside of
 512-byte region [ffff8881eb2cf000, ffff8881eb2cf200)
The buggy address belongs to the page:
page:ffffea0007acb300 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 0x1d2a20(GFP_ATOMIC|__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+0x18f/0x370 mm/page_alloc.c:2171
 get_page_from_freelist+0x2d13/0x2d90 mm/page_alloc.c:3794
 __alloc_pages_nodemask+0x393/0x840 mm/page_alloc.c:4893
 alloc_slab_page+0x39/0x3c0 mm/slub.c:343
 allocate_slab mm/slub.c:1683 [inline]
 new_slab+0x97/0x440 mm/slub.c:1749
 new_slab_objects mm/slub.c:2505 [inline]
 ___slab_alloc+0x2fe/0x490 mm/slub.c:2667
 __slab_alloc+0x62/0xa0 mm/slub.c:2707
 slab_alloc_node mm/slub.c:2792 [inline]
 slab_alloc mm/slub.c:2837 [inline]
 __kmalloc_track_caller+0x16d/0x2b0 mm/slub.c:4449
 __kmalloc_reserve net/core/skbuff.c:142 [inline]
 __alloc_skb+0xb4/0x4d0 net/core/skbuff.c:210
 alloc_skb include/linux/skbuff.h:1080 [inline]
 nlmsg_new include/net/netlink.h:888 [inline]
 inet6_ifa_notify net/ipv6/addrconf.c:5457 [inline]
 __ipv6_ifa_notify+0x2e1/0x1290 net/ipv6/addrconf.c:6066
 ipv6_ifa_notify net/ipv6/addrconf.c:6119 [inline]
 addrconf_dad_completed+0x181/0xdb0 net/ipv6/addrconf.c:4232
 addrconf_dad_work+0xe4d/0x16f0 net/ipv6/addrconf.c:4036
 process_one_work+0x765/0xd20 kernel/workqueue.c:2290
 worker_thread+0xaef/0x1470 kernel/workqueue.c:2436
 kthread+0x2da/0x360 kernel/kthread.c:288
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:354
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+0x847/0x950 mm/page_alloc.c:1438
 free_the_page mm/page_alloc.c:4955 [inline]
 __free_pages+0x91/0x140 mm/page_alloc.c:4961
 device_release+0x6b/0x190 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+0x1e6/0x2f0 lib/kobject.c:764
 tun_set_iff+0x870/0xdc0 drivers/net/tun.c:2919
 __tun_chr_ioctl+0x8a9/0x1d00 drivers/net/tun.c:3182
 do_vfs_ioctl+0x742/0x1720 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+0xd4/0x110 fs/ioctl.c:747
 do_syscall_64+0xca/0x1c0 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x5c/0xc1

Memory state around the buggy address:
 ffff8881eb2cf080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881eb2cf100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881eb2cf180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                              ^
 ffff8881eb2cf200: fc fc