==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
BUG: KASAN: use-after-free in atomic64_try_cmpxchg_acquire include/asm-generic/atomic-instrumented.h:1515 [inline]
BUG: KASAN: use-after-free in atomic_long_try_cmpxchg_acquire include/asm-generic/atomic-long.h:443 [inline]
BUG: KASAN: use-after-free in __mutex_trylock_fast kernel/locking/mutex.c:173 [inline]
BUG: KASAN: use-after-free in mutex_lock+0x85/0xf0 kernel/locking/mutex.c:298
Write of size 8 at addr ffff88810ef14550 by task syz.5.518/2632

CPU: 1 PID: 2632 Comm: syz.5.518 Not tainted 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
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x249/0x2a0 mm/kasan/generic.c:189
 __kasan_check_write+0x14/0x20 mm/kasan/shadow.c:37
 instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
 atomic64_try_cmpxchg_acquire include/asm-generic/atomic-instrumented.h:1515 [inline]
 atomic_long_try_cmpxchg_acquire include/asm-generic/atomic-long.h:443 [inline]
 __mutex_trylock_fast kernel/locking/mutex.c:173 [inline]
 mutex_lock+0x85/0xf0 kernel/locking/mutex.c:298
 pppol2tp_release+0x178/0x2b0 net/l2tp/l2tp_ppp.c:442
 __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: 0033:0x7f0779bb3199
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:00007ffdc4e56eb8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007f0779e3cda0 RCX: 00007f0779bb3199
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f0779e3cda0 R08: 0000000000000006 R09: 0000000000000000
R10: 00007f0779e3ccb0 R11: 0000000000000246 R12: 000000000001b3a7
R13: 00007f0779e3afac R14: 000000000001b342 R15: 00007ffdc4e56fc0

Allocated by task 2633:
 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 2632:
 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
 pppol2tp_release+0x169/0x2b0 net/l2tp/l2tp_ppp.c:439
 __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

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
 neigh_destroy+0x445/0x570 net/core/neighbour.c:861
 neigh_release include/net/neighbour.h:427 [inline]
 neigh_cleanup_and_release+0x76/0x1a0 net/core/neighbour.c:104
 neigh_flush_dev+0x624/0x810 net/core/neighbour.c:375
 __neigh_ifdown+0x3f/0x380 net/core/neighbour.c:392
 neigh_ifdown+0x1f/0x30 net/core/neighbour.c:409
 rt6_disable_ip+0x714/0x7a0 net/ipv6/route.c:4800
 addrconf_ifdown+0x144/0x1890 net/ipv6/addrconf.c:3794
 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]
 dev_close_many+0x328/0x4d0 net/core/dev.c:1653
 unregister_netdevice_many+0x477/0x19f0 net/core/dev.c:10755
 default_device_exit_batch+0x35e/0x3c0 net/core/dev.c:11298
 ops_exit_list net/core/net_namespace.c:190 [inline]
 cleanup_net+0x5fe/0xb80 net/core/net_namespace.c:609
 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

The buggy address belongs to the object at ffff88810ef14400
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 336 bytes inside of
 512-byte region [ffff88810ef14400, ffff88810ef14600)
The buggy address belongs to the page:
page:ffffea00043bc500 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10ef14
head:ffffea00043bc500 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 0000000000000000 0000000100000001 ffff888100043080
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 0x152a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_HARDWALL), pid 316, ts 26001287504, free_ts 25613673705
 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+0x1f9/0x330 mm/slub.c:4034
 kmalloc include/linux/slab.h:560 [inline]
 kzalloc include/linux/slab.h:667 [inline]
 neigh_alloc net/core/neighbour.c:439 [inline]
 ___neigh_create+0x6ec/0x1a70 net/core/neighbour.c:592
 __neigh_create+0x31/0x40 net/core/neighbour.c:680
 ip6_finish_output2+0x8fe/0x1540 net/ipv6/ip6_output.c:129
 __ip6_finish_output+0x5fd/0x790 net/ipv6/ip6_output.c:203
 ip6_finish_output+0x33/0x1e0 net/ipv6/ip6_output.c:213
 NF_HOOK_COND include/linux/netfilter.h:288 [inline]
 ip6_output+0x1fa/0x420 net/ipv6/ip6_output.c:236
 dst_output include/net/dst.h:451 [inline]
 NF_HOOK include/linux/netfilter.h:299 [inline]
 ndisc_send_skb+0x721/0xbc0 net/ipv6/ndisc.c:513
 ndisc_send_ns+0x879/0xb10 net/ipv6/ndisc.c:655
 addrconf_dad_work+0xa40/0x1480 net/ipv6/addrconf.c:4216
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_slab+0xcf/0x190 mm/slub.c:1899
 free_slab mm/slub.c:1914 [inline]
 discard_slab mm/slub.c:1920 [inline]
 unfreeze_partials+0x150/0x180 mm/slub.c:2415
 put_cpu_partial+0xc1/0x180 mm/slub.c:2451
 __slab_free+0x2c9/0x3a0 mm/slub.c:3100
 do_slab_free mm/slub.c:3196 [inline]
 ___cache_free+0x10e/0x130 mm/slub.c:3215
 qlink_free+0x50/0x90 mm/kasan/quarantine.c:157
 qlist_free_all+0x5f/0xb0 mm/kasan/quarantine.c:176
 kasan_quarantine_reduce+0x14a/0x160 mm/kasan/quarantine.c:283
 __kasan_slab_alloc+0x2f/0xe0 mm/kasan/common.c:440
 kasan_slab_alloc include/linux/kasan.h:244 [inline]
 slab_post_alloc_hook+0x5d/0x2f0 mm/slab.h:580
 slab_alloc_node mm/slub.c:2952 [inline]
 slab_alloc mm/slub.c:2960 [inline]
 kmem_cache_alloc_trace+0x155/0x2e0 mm/slub.c:2977
 kmalloc include/linux/slab.h:555 [inline]
 kzalloc include/linux/slab.h:667 [inline]
 kset_create lib/kobject.c:982 [inline]
 kset_create_and_add+0x59/0x2c0 lib/kobject.c:1025
 register_queue_kobjects net/core/net-sysfs.c:1742 [inline]
 netdev_register_kobject+0x1be/0x330 net/core/net-sysfs.c:2001
 register_netdevice+0xdae/0x13a0 net/core/dev.c:10067

Memory state around the buggy address:
 ffff88810ef14400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88810ef14480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88810ef14500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                 ^
 ffff88810ef14580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88810ef14600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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