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BUG: KASAN: slab-out-of-bounds in __write_once_size include/linux/compiler.h:295 [inline]
BUG: KASAN: slab-out-of-bounds in __hlist_del include/linux/list.h:789 [inline]
BUG: KASAN: slab-out-of-bounds in detach_timer kernel/time/timer.c:824 [inline]
BUG: KASAN: slab-out-of-bounds in detach_if_pending+0x160/0x360 kernel/time/timer.c:841
Write of size 8 at addr ffff8881d85db1c0 by task syz-executor.2/480

CPU: 1 PID: 480 Comm: syz-executor.2 Not tainted 5.4.259-syzkaller-04797-g1303f659c2b1 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/10/2023
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
 __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+0x160/0x360 kernel/time/timer.c:841
 try_to_del_timer_sync kernel/time/timer.c:1238 [inline]
 del_timer_sync+0x13c/0x230 kernel/time/timer.c:1379
 tun_flow_uninit+0x2c/0x280 drivers/net/tun.c:1451
 tun_free_netdev+0x77/0x190 drivers/net/tun.c:2401
 netdev_run_todo+0xb7f/0xdf0 net/core/dev.c:9450
 tun_detach drivers/net/tun.c:765 [inline]
 tun_chr_close+0xc1/0x130 drivers/net/tun.c:3557
 __fput+0x262/0x680 fs/file_table.c:281
 task_work_run+0x140/0x170 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x190/0x1a0 arch/x86/entry/common.c:163
 prepare_exit_to_usermode+0x199/0x200 arch/x86/entry/common.c:194
 entry_SYSCALL_64_after_hwframe+0x5c/0xc1

Allocated by task 0:
(stack is not available)

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff8881d85db000
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 448 bytes inside of
 512-byte region [ffff8881d85db000, ffff8881d85db200)
The buggy address belongs to the page:
page:ffffea0007617600 refcount:1 mapcount:0 mapping:ffff8881f5c02500 index:0x0 compound_mapcount: 0
flags: 0x8000000000010200(slab|head)
raw: 8000000000010200 dead000000000100 dead000000000122 ffff8881f5c02500
raw: 0000000000000000 0000000080100010 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC)
 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:4891
 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_netconf_notify_devconf+0xc9/0x180 net/ipv6/addrconf.c:573
 __addrconf_sysctl_unregister net/ipv6/addrconf.c:6983 [inline]
 addrconf_sysctl_unregister net/ipv6/addrconf.c:7007 [inline]
 addrconf_ifdown+0x17cc/0x1a90 net/ipv6/addrconf.c:3910
 addrconf_notify+0x375/0xe50 net/ipv6/addrconf.c:3681
 notifier_call_chain kernel/notifier.c:98 [inline]
 __raw_notifier_call_chain kernel/notifier.c:399 [inline]
 raw_notifier_call_chain+0x95/0x110 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]
 rollback_registered_many+0xce5/0x1330 net/core/dev.c:8623
 rollback_registered net/core/dev.c:8665 [inline]
 unregister_netdevice_queue+0x333/0x500 net/core/dev.c:9759
 unregister_netdevice include/linux/netdevice.h:2726 [inline]
 __tun_detach+0x8cd/0x1360 drivers/net/tun.c:746
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:4953 [inline]
 __free_pages+0x91/0x140 mm/page_alloc.c:4959
 device_release+0x6b/0x190 drivers/base/core.c:1776
 kobject_cleanup lib/kobject.c:708 [inline]
 kobject_release lib/kobject.c:739 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x1e6/0x2f0 lib/kobject.c:756
 netdev_run_todo+0xc44/0xdf0 net/core/dev.c:9461
 tun_detach drivers/net/tun.c:765 [inline]
 tun_chr_close+0xc1/0x130 drivers/net/tun.c:3557
 __fput+0x262/0x680 fs/file_table.c:281
 task_work_run+0x140/0x170 kernel/task_work.c:113
 get_signal+0x13c6/0x1440 kernel/signal.c:2529
 do_signal+0xb0/0x11f0 arch/x86/kernel/signal.c:809
 exit_to_usermode_loop+0xc0/0x1a0 arch/x86/entry/common.c:159
 prepare_exit_to_usermode+0x199/0x200 arch/x86/entry/common.c:194
 entry_SYSCALL_64_after_hwframe+0x5c/0xc1

Memory state around the buggy address:
 ffff8881d85db080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8881d85db100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8881d85db180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                           ^
 ffff8881d85db200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8881d85db280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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