================================================================== BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75 Read of size 8 at addr ffff88810babcd90 by task kworker/u4:5/3163 CPU: 0 PID: 3163 Comm: kworker/u4:5 Tainted: G W syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026 Workqueue: netns cleanup_net 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 rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75 rcu_do_batch+0x448/0xaf0 kernel/rcu/tree.c:2484 rcu_core+0x50a/0xca0 kernel/rcu/tree.c:2735 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2748 __do_softirq+0x255/0x563 kernel/softirq.c:309 asm_call_irq_on_stack+0xf/0x20 __run_on_irqstack arch/x86/include/asm/irq_stack.h:26 [inline] run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:77 [inline] do_softirq_own_stack+0x60/0x80 arch/x86/kernel/irq_64.c:77 invoke_softirq kernel/softirq.c:405 [inline] __irq_exit_rcu+0x128/0x150 kernel/softirq.c:435 irq_exit_rcu+0x9/0x10 kernel/softirq.c:447 sysvec_apic_timer_interrupt+0xbf/0xe0 arch/x86/kernel/apic/apic.c:1106 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:635 RIP: 0010:__kasan_check_write+0x4/0x20 mm/kasan/shadow.c:37 Code: 31 ff eb d1 00 00 55 48 89 e5 89 f6 48 8b 4d 08 31 d2 e8 af ed ff ff 5d c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 55 48 89 e5 <89> f6 48 8b 4d 08 ba 01 00 00 00 e8 8c ed ff ff 5d c3 66 2e 0f 1f RSP: 0018:ffffc90000f1f838 EFLAGS: 00000282 RAX: ffffffff81c752d9 RBX: ffff888125fcc680 RCX: ffff8881187cd000 RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff888125fcc680 RBP: ffffc90000f1f838 R08: ffff888125fcc683 R09: 1ffff11024bf98d0 R10: dffffc0000000000 R11: ffffed1024bf98d1 R12: ffff888125fcc270 R13: dffffc0000000000 R14: ffff888125fcc680 R15: 0000000000000001 instrument_atomic_read_write include/linux/instrumented.h:101 [inline] atomic_dec_and_test include/asm-generic/atomic-instrumented.h:748 [inline] kernfs_put+0x2f/0x480 fs/kernfs/dir.c:521 kernfs_remove_by_name_ns+0xea/0x160 fs/kernfs/dir.c:1599 kernfs_remove_by_name include/linux/kernfs.h:623 [inline] remove_files fs/sysfs/group.c:28 [inline] sysfs_remove_group+0x108/0x290 fs/sysfs/group.c:289 netdev_queue_update_kobjects+0x31e/0x390 net/core/net-sysfs.c:1707 remove_queue_kobjects net/core/net-sysfs.c:1806 [inline] netdev_unregister_kobject+0x104/0x260 net/core/net-sysfs.c:1959 unregister_netdevice_many+0x14c6/0x19f0 net/core/dev.c:10806 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 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 Allocated by task 4146: 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 9: 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 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 Second to 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 fib6_info_release include/net/ip6_fib.h:346 [inline] __ip6_del_rt+0xf5/0x150 net/ipv6/route.c:3798 ip6_del_rt+0xbe/0x110 net/ipv6/route.c:3809 __ipv6_ifa_notify+0x872/0xe70 net/ipv6/addrconf.c:6204 addrconf_ifdown+0xdb1/0x1890 net/ipv6/addrconf.c:3926 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:10756 ip6gre_exit_batch_net+0x5ca/0x620 net/ipv6/ip6_gre.c:1634 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 ffff88810babcc00 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 400 bytes inside of 512-byte region [ffff88810babcc00, ffff88810babce00) The buggy address belongs to the page: page:ffffea00042eaf00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10babc head:ffffea00042eaf00 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 0x52a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 280, ts 23383261735, free_ts 23302872376 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] fib6_info_alloc+0x34/0xe0 net/ipv6/ip6_fib.c:154 ip6_route_info_create+0x4c7/0x1450 net/ipv6/route.c:3675 addrconf_f6i_alloc+0x19c/0x3f0 net/ipv6/route.c:4474 fixup_permanent_addr net/ipv6/addrconf.c:3518 [inline] addrconf_permanent_addr+0x237/0x940 net/ipv6/addrconf.c:3557 addrconf_notify+0x752/0xea0 net/ipv6/addrconf.c:3625 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_notify_flags+0x2f4/0x5b0 net/core/dev.c:8584 dev_change_flags+0xe3/0x1a0 net/core/dev.c:8622 do_setlink+0xb19/0x29a0 net/core/rtnetlink.c:2744 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] __kmalloc+0x17b/0x330 mm/slub.c:4034 kmalloc include/linux/slab.h:560 [inline] kzalloc include/linux/slab.h:667 [inline] fib6_info_alloc+0x34/0xe0 net/ipv6/ip6_fib.c:154 ip6_route_info_create+0x4c7/0x1450 net/ipv6/route.c:3675 ip6_route_add+0x27/0x130 net/ipv6/route.c:3771 Memory state around the buggy address: ffff88810babcc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88810babcd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88810babcd80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88810babce00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88810babce80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ================================================================== ---------------- Code disassembly (best guess): 0: 31 ff xor %edi,%edi 2: eb d1 jmp 0xffffffd5 4: 00 00 add %al,(%rax) 6: 55 push %rbp 7: 48 89 e5 mov %rsp,%rbp a: 89 f6 mov %esi,%esi c: 48 8b 4d 08 mov 0x8(%rbp),%rcx 10: 31 d2 xor %edx,%edx 12: e8 af ed ff ff call 0xffffedc6 17: 5d pop %rbp 18: c3 ret 19: 66 2e 0f 1f 84 00 00 cs nopw 0x0(%rax,%rax,1) 20: 00 00 00 23: 0f 1f 00 nopl (%rax) 26: 55 push %rbp 27: 48 89 e5 mov %rsp,%rbp * 2a: 89 f6 mov %esi,%esi <-- trapping instruction 2c: 48 8b 4d 08 mov 0x8(%rbp),%rcx 30: ba 01 00 00 00 mov $0x1,%edx 35: e8 8c ed ff ff call 0xffffedc6 3a: 5d pop %rbp 3b: c3 ret 3c: 66 data16 3d: 2e cs 3e: 0f .byte 0xf 3f: 1f (bad)