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BUG: KASAN: use-after-free in rcu_segcblist_enqueue+0x85/0xa0 kernel/rcu/rcu_segcblist.c:250
Write of size 8 at addr ffff8881163cdd90 by task syz.0.99/809

CPU: 0 PID: 809 Comm: syz.0.99 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
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_store8_noabort+0x17/0x20 mm/kasan/report_generic.c:314
 rcu_segcblist_enqueue+0x85/0xa0 kernel/rcu/rcu_segcblist.c:250
 __call_rcu kernel/rcu/tree.c:2998 [inline]
 call_rcu+0x4df/0x1090 kernel/rcu/tree.c:3054
 security_inode_free+0xb4/0xd0 security/security.c:984
 __destroy_inode+0x175/0x4f0 fs/inode.c:258
 destroy_inode fs/inode.c:281 [inline]
 evict+0x7e8/0x940 fs/inode.c:629
 iput_final fs/inode.c:1736 [inline]
 iput+0x654/0x7e0 fs/inode.c:1762
 dentry_unlink_inode+0x2d5/0x390 fs/dcache.c:378
 __dentry_kill+0x45b/0x660 fs/dcache.c:583
 dentry_kill+0xc0/0x2a0 fs/dcache.c:-1
 dput+0x42/0x80 fs/dcache.c:883
 __fput+0x4bd/0x730 fs/file_table.c:294
 ____fput+0x15/0x20 fs/file_table.c:314
 task_work_run+0x127/0x190 kernel/task_work.c:189
 exit_task_work include/linux/task_work.h:33 [inline]
 do_exit+0xa7c/0x24e0 kernel/exit.c:879
 do_group_exit+0x149/0x310 kernel/exit.c:993
 get_signal+0xfb1/0x1300 kernel/signal.c:2806
 arch_do_signal_or_restart+0xe7/0x11b0 arch/x86/kernel/signal.c:805
 handle_signal_work kernel/entry/common.c:148 [inline]
 exit_to_user_mode_loop+0xa2/0xe0 kernel/entry/common.c:172
 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: 0033:0x7fd094c9eb19
Code: Unable to access opcode bytes at RIP 0x7fd094c9eaef.
RSP: 002b:00007fd0936f6028 EFLAGS: 00000246 ORIG_RAX: 000000000000002f
RAX: fffffffffffffe00 RBX: 00007fd094f24fa0 RCX: 00007fd094c9eb19
RDX: 0000000000000002 RSI: 00002000000008c0 RDI: 0000000000000005
RBP: 00007fd094d36af8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd094f25038 R14: 00007fd094f24fa0 R15: 00007ffe5a01da28

Allocated by task 809:
 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 192:
 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
 __call_rcu kernel/rcu/tree.c:2980 [inline]
 call_rcu+0x11a/0x1090 kernel/rcu/tree.c:3054
 pppol2tp_release+0x1e3/0x2b0 net/l2tp/l2tp_ppp.c:447
 __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
 exit_task_work include/linux/task_work.h:33 [inline]
 do_exit+0xa7c/0x24e0 kernel/exit.c:879
 do_group_exit+0x149/0x310 kernel/exit.c:993
 get_signal+0xfb1/0x1300 kernel/signal.c:2806
 arch_do_signal_or_restart+0xe7/0x11b0 arch/x86/kernel/signal.c:805
 handle_signal_work kernel/entry/common.c:148 [inline]
 exit_to_user_mode_loop+0xa2/0xe0 kernel/entry/common.c:172
 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 ffff8881163cdc00
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
 512-byte region [ffff8881163cdc00, ffff8881163cde00)
The buggy address belongs to the page:
page:ffffea000458f300 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1163cc
head:ffffea000458f300 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 dead000000000100 dead000000000122 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 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 7, ts 35120525898, free_ts 34705907384
 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]
 inet_netconf_notify_devconf+0x169/0x220 net/ipv4/devinet.c:2120
 __devinet_sysctl_unregister net/ipv4/devinet.c:2625 [inline]
 devinet_sysctl_unregister net/ipv4/devinet.c:2649 [inline]
 inetdev_destroy net/ipv4/devinet.c:326 [inline]
 inetdev_event+0x7b0/0x1010 net/ipv4/devinet.c:1612
 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:10779
 ip_tunnel_delete_nets+0x343/0x390 net/ipv4/ip_tunnel.c:1122
 ipgre_exit_batch_net+0x22/0x30 net/ipv4/ip_gre.c:1041
 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
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_pcp_prepare mm/page_alloc.c:1421 [inline]
 free_unref_page_prepare+0x2b7/0x2d0 mm/page_alloc.c:3336
 free_unref_page_list+0x129/0x9c0 mm/page_alloc.c:3443
 release_pages+0xe41/0xe90 mm/swap.c:1103
 free_pages_and_swap_cache+0x86/0xa0 mm/swap_state.c:356
 tlb_batch_pages_flush mm/mmu_gather.c:49 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:240 [inline]
 tlb_flush_mmu mm/mmu_gather.c:247 [inline]
 tlb_finish_mmu+0x17e/0x310 mm/mmu_gather.c:326
 exit_mmap+0x329/0x590 mm/mmap.c:3387
 __mmput+0x92/0x2d0 kernel/fork.c:1153
 mmput+0x4e/0x150 kernel/fork.c:1176
 exit_mm kernel/exit.c:546 [inline]
 do_exit+0x9d8/0x24e0 kernel/exit.c:866
 __do_sys_exit kernel/exit.c:962 [inline]
 __se_sys_exit kernel/exit.c:960 [inline]
 __ia32_sys_exit+0x0/0x40 kernel/exit.c:960
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Memory state around the buggy address:
 ffff8881163cdc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881163cdd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881163cdd80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff8881163cde00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8881163cde80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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