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BUG: KASAN: use-after-free in pppol2tp_release+0x192/0x2b0 net/l2tp/l2tp_ppp.c:443
Read of size 8 at addr ffff888110123980 by task syz.9.385/2184

CPU: 0 PID: 2184 Comm: syz.9.385 Tainted: G        W         syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
Call Trace:
 __dump_stack+0x21/0x24 lib/dump_stack.c:77
 dump_stack_lvl+0x1a7/0x208 lib/dump_stack.c:118
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:435 [inline]
 kasan_report+0x100/0x140 mm/kasan/report.c:452
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:309
 pppol2tp_release+0x192/0x2b0 net/l2tp/l2tp_ppp.c:443
 __sock_release net/socket.c:597 [inline]
 sock_close+0xb8/0x200 net/socket.c:1287
 __fput+0x2dc/0x730 fs/file_table.c:281
 ____fput+0x15/0x20 fs/file_table.c:314
 task_work_run+0x127/0x190 kernel/task_work.c:189
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop+0xcb/0xe0 kernel/entry/common.c:175
 exit_to_user_mode_prepare+0x76/0xa0 kernel/entry/common.c:202
 syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:277
 do_syscall_64+0x3d/0x40 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7faf6d4c31d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd37580c28 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007faf6d74cda0 RCX: 00007faf6d4c31d9
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007faf6d74cda0 R08: 0000000000000006 R09: 0000000000000000
R10: 00007faf6d74ccb0 R11: 0000000000000246 R12: 0000000000015e1d
R13: 00007faf6d74b09c R14: 0000000000015b68 R15: 00007faf6d74b090

Allocated by task 2185:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:430 [inline]
 ____kasan_kmalloc mm/kasan/common.c:509 [inline]
 __kasan_kmalloc+0xd4/0x100 mm/kasan/common.c:518
 kasan_kmalloc include/linux/kasan.h:254 [inline]
 __kmalloc+0x19f/0x330 mm/slub.c:4038
 kmalloc include/linux/slab.h:560 [inline]
 kzalloc include/linux/slab.h:667 [inline]
 l2tp_session_create+0x39/0xb60 net/l2tp/l2tp_core.c:1616
 pppol2tp_connect+0xbf5/0x1640 net/l2tp/l2tp_ppp.c:772
 __sys_connect_file net/socket.c:1867 [inline]
 __sys_connect+0x3ce/0x450 net/socket.c:1884
 __do_sys_connect net/socket.c:1894 [inline]
 __se_sys_connect net/socket.c:1891 [inline]
 __x64_sys_connect+0x7a/0x90 net/socket.c:1891
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Freed by task 674:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4a/0x70 mm/kasan/common.c:45
 kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
 ____kasan_slab_free+0x125/0x160 mm/kasan/common.c:362
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:370
 kasan_slab_free include/linux/kasan.h:220 [inline]
 slab_free_hook mm/slub.c:1600 [inline]
 slab_free_freelist_hook+0xc5/0x190 mm/slub.c:1626
 slab_free mm/slub.c:3208 [inline]
 kfree+0xc0/0x270 mm/slub.c:4196
 l2tp_session_free net/l2tp/l2tp_core.c:168 [inline]
 l2tp_session_put+0xb2/0x1a0 net/l2tp/l2tp_core.c:193
 l2tp_session_delete+0x3a9/0x4a0 net/l2tp/l2tp_core.c:1589
 l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1235 [inline]
 l2tp_tunnel_del_work+0x180/0x3d0 net/l2tp/l2tp_core.c:1273
 process_one_work+0x6fd/0xbc0 kernel/workqueue.c:2301
 worker_thread+0xa8e/0x13c0 kernel/workqueue.c:2447
 kthread+0x324/0x3b0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

Last potentially related work creation:
 kasan_save_stack+0x3a/0x60 mm/kasan/common.c:38
 __kasan_record_aux_stack+0xd2/0x100 mm/kasan/generic.c:348
 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358
 kvfree_call_rcu+0x117/0x670 kernel/rcu/tree.c:3539
 drop_sysctl_table+0x2f5/0x430 fs/proc/proc_sysctl.c:1684
 drop_sysctl_table+0x2e4/0x430 fs/proc/proc_sysctl.c:1687
 unregister_sysctl_table+0x75/0x120 fs/proc/proc_sysctl.c:1722
 unregister_net_sysctl_table+0x15/0x20 net/sysctl_net.c:127
 __addrconf_sysctl_unregister net/ipv6/addrconf.c:7108 [inline]
 addrconf_sysctl_unregister net/ipv6/addrconf.c:7136 [inline]
 addrconf_ifdown+0x1597/0x1890 net/ipv6/addrconf.c:3946
 addrconf_notify+0x3bd/0xea0 net/ipv6/addrconf.c:-1
 notifier_call_chain kernel/notifier.c:83 [inline]
 raw_notifier_call_chain+0x90/0x100 kernel/notifier.c:410
 call_netdevice_notifiers_info net/core/dev.c:2052 [inline]
 call_netdevice_notifiers_extack net/core/dev.c:2064 [inline]
 call_netdevice_notifiers net/core/dev.c:2078 [inline]
 unregister_netdevice_many+0x100e/0x19f0 net/core/dev.c:10778
 unregister_netdevice_queue+0x2e1/0x320 net/core/dev.c:10712
 unregister_netdevice include/linux/netdevice.h:2939 [inline]
 __tun_detach+0xc9d/0x1450 drivers/net/tun.c:697
 tun_detach drivers/net/tun.c:713 [inline]
 tun_chr_close+0x92/0x140 drivers/net/tun.c:3500
 __fput+0x2dc/0x730 fs/file_table.c:281
 ____fput+0x15/0x20 fs/file_table.c:314
 task_work_run+0x127/0x190 kernel/task_work.c:189
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop+0xcb/0xe0 kernel/entry/common.c:175
 exit_to_user_mode_prepare+0x76/0xa0 kernel/entry/common.c:202
 syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:277
 do_syscall_64+0x3d/0x40 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

The buggy address belongs to the object at ffff888110123800
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 384 bytes inside of
 512-byte region [ffff888110123800, ffff888110123a00)
The buggy address belongs to the page:
page:ffffea0004404800 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888110123400 pfn:0x110120
head:ffffea0004404800 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 ffffea00049c3808 ffffea000433af08 ffff888100043080
raw: ffff888110123400 0000000000100005 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), pid 365, ts 26110073729, free_ts 26106592250
 set_page_owner include/linux/page_owner.h:35 [inline]
 post_alloc_hook mm/page_alloc.c:2456 [inline]
 prep_new_page+0x176/0x190 mm/page_alloc.c:2462
 get_page_from_freelist+0x225f/0x23f0 mm/page_alloc.c:4254
 __alloc_pages_nodemask+0x29a/0x640 mm/page_alloc.c:5384
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1813 [inline]
 new_slab+0x84/0x3f0 mm/slub.c:1874
 new_slab_objects mm/slub.c:2632 [inline]
 ___slab_alloc+0x2f8/0x4c0 mm/slub.c:2796
 __slab_alloc+0x63/0xa0 mm/slub.c:2836
 slab_alloc_node mm/slub.c:2918 [inline]
 slab_alloc mm/slub.c:2960 [inline]
 __kmalloc_track_caller+0x1e4/0x310 mm/slub.c:4541
 __kmalloc_reserve net/core/skbuff.c:144 [inline]
 __alloc_skb+0xdc/0x520 net/core/skbuff.c:212
 alloc_skb include/linux/skbuff.h:1126 [inline]
 nlmsg_new include/net/netlink.h:953 [inline]
 inet6_ifa_notify net/ipv6/addrconf.c:5533 [inline]
 __ipv6_ifa_notify+0x200/0xe70 net/ipv6/addrconf.c:6156
 ipv6_ifa_notify net/ipv6/addrconf.c:6209 [inline]
 addrconf_dad_completed+0x18c/0xe30 net/ipv6/addrconf.c:4254
 addrconf_dad_work+0xc5f/0x1480 net/ipv6/addrconf.c:-1
 process_one_work+0x6fd/0xbc0 kernel/workqueue.c:2301
 worker_thread+0xa8e/0x13c0 kernel/workqueue.c:2447
 kthread+0x324/0x3b0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:28 [inline]
 free_pages_prepare mm/page_alloc.c:1349 [inline]
 __free_pages_ok+0x80b/0x830 mm/page_alloc.c:1629
 free_the_page mm/page_alloc.c:5445 [inline]
 __free_pages+0xd8/0x390 mm/page_alloc.c:5454
 free_pages+0x82/0x90 mm/page_alloc.c:5465
 __stack_depot_save+0x492/0x4c0 lib/stackdepot.c:359
 kasan_save_stack mm/kasan/common.c:39 [inline]
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:430 [inline]
 ____kasan_kmalloc mm/kasan/common.c:509 [inline]
 __kasan_kmalloc+0xe6/0x100 mm/kasan/common.c:518
 kasan_kmalloc include/linux/kasan.h:254 [inline]
 kmem_cache_alloc_trace+0x179/0x2e0 mm/slub.c:2979
 kmalloc include/linux/slab.h:555 [inline]
 usb_control_msg+0x74/0x3f0 drivers/usb/core/message.c:156
 get_port_status drivers/usb/core/hub.c:595 [inline]
 hub_ext_port_status+0xf2/0x6a0 drivers/usb/core/hub.c:612
 hub_port_status drivers/usb/core/hub.c:634 [inline]
 hub_activate+0x8a3/0x1a70 drivers/usb/core/hub.c:1150
 hub_resume+0x98/0x330 drivers/usb/core/hub.c:3968
 usb_resume_interface drivers/usb/core/driver.c:1363 [inline]
 usb_resume_both+0x729/0xd40 drivers/usb/core/driver.c:1534
 usb_runtime_resume+0x21/0x30 drivers/usb/core/driver.c:1991
 __rpm_callback+0x300/0x750 drivers/base/power/runtime.c:394
 rpm_callback drivers/base/power/runtime.c:534 [inline]
 rpm_resume+0x1084/0x1c40 drivers/base/power/runtime.c:909
 __pm_runtime_resume+0x69/0x90 drivers/base/power/runtime.c:1140
 pm_runtime_get_sync include/linux/pm_runtime.h:398 [inline]
 usb_autoresume_device+0x23/0x60 drivers/usb/core/driver.c:1721

Memory state around the buggy address:
 ffff888110123880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888110123900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888110123980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff888110123a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888110123a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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