================================================================== BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75 Read of size 8 at addr ffff88810b435d90 by task kworker/1:5/362 CPU: 1 PID: 362 Comm: kworker/1:5 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 Workqueue: rcu_gp srcu_invoke_callbacks 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 do_softirq+0xb0/0xf0 kernel/softirq.c:358 __local_bh_enable_ip+0x70/0x80 kernel/softirq.c:194 local_bh_enable+0x15/0x20 include/linux/bottom_half.h:32 srcu_invoke_callbacks+0x198/0x380 kernel/rcu/srcutree.c:1259 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 804: 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 741: 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:172 exit_to_user_mode_prepare+0x76/0xa0 kernel/entry/common.c:199 syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:274 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 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_del net/core/neighbour.c:198 [inline] neigh_remove_one+0x343/0x3b0 net/core/neighbour.c:219 neigh_forced_gc net/core/neighbour.c:252 [inline] neigh_alloc net/core/neighbour.c:430 [inline] ___neigh_create+0x48d/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:127 __ip6_finish_output+0x5fd/0x790 net/ipv6/ip6_output.c:201 ip6_finish_output+0x33/0x1e0 net/ipv6/ip6_output.c:211 NF_HOOK_COND include/linux/netfilter.h:288 [inline] ip6_output+0x1fa/0x420 net/ipv6/ip6_output.c:234 dst_output include/net/dst.h:451 [inline] NF_HOOK include/linux/netfilter.h:299 [inline] mld_sendpack+0x61e/0xb00 net/ipv6/mcast.c:1676 mld_send_initial_cr+0x246/0x2b0 net/ipv6/mcast.c:2093 ipv6_mc_dad_complete+0x76/0x3c0 net/ipv6/mcast.c:2100 addrconf_dad_completed+0x74c/0xe30 net/ipv6/addrconf.c:4273 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 The buggy address belongs to the object at ffff88810b435c00 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 400 bytes inside of 512-byte region [ffff88810b435c00, ffff88810b435e00) The buggy address belongs to the page: page:ffffea00042d0d00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10b434 head:ffffea00042d0d00 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, ts 2367932760, free_ts 2367114520 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_register+0x31c/0x390 net/ipv4/devinet.c:2604 devinet_sysctl_register+0x169/0x1e0 net/ipv4/devinet.c:2638 inetdev_init+0x26c/0x490 net/ipv4/devinet.c:277 inetdev_event+0x1f4/0x1010 net/ipv4/devinet.c:1544 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+0x119/0x190 net/core/dev.c:2078 register_netdevice+0x100a/0x13a0 net/core/dev.c:10098 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] kzalloc include/linux/slab.h:667 [inline] call_usermodehelper_setup+0x71/0x1d0 kernel/umh.c:363 kobject_uevent_env+0x636/0x700 lib/kobject_uevent.c:629 kobject_uevent+0x1d/0x30 lib/kobject_uevent.c:657 device_add+0x7d2/0xc00 drivers/base/core.c:3254 netdev_register_kobject+0x18e/0x330 net/core/net-sysfs.c:1997 register_netdevice+0xdae/0x13a0 net/core/dev.c:10067 dummy_init_one+0x75/0xb7 drivers/net/dummy.c:170 dummy_init_module+0x6f/0xfe drivers/net/dummy.c:191 do_one_initcall+0x205/0x5e0 init/main.c:1211 do_initcall_level+0x174/0x2dc init/main.c:1284 Memory state around the buggy address: ffff88810b435c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88810b435d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88810b435d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88810b435e00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88810b435e80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ==================================================================