================================================================== BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75 Read of size 8 at addr ffff88812682c990 by task ksoftirqd/1/25 CPU: 1 PID: 25 Comm: ksoftirqd/1 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026 Call Trace: __dump_stack+0x21/0x30 lib/dump_stack.c:88 dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248 __kasan_report mm/kasan/report.c:427 [inline] kasan_report+0x10f/0x150 mm/kasan/report.c:444 __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+0x47d/0xbf0 kernel/rcu/tree.c:2512 rcu_core+0x4a3/0xef0 kernel/rcu/tree.c:2763 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2776 handle_softirqs+0x250/0x560 kernel/softirq.c:583 run_ksoftirqd+0x28/0x40 kernel/softirq.c:959 smpboot_thread_fn+0x446/0x880 kernel/smpboot.c:164 kthread+0x3f5/0x4f0 kernel/kthread.c:337 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 Allocated by task 7783: 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:433 [inline] ____kasan_kmalloc mm/kasan/common.c:512 [inline] __kasan_kmalloc+0xd4/0x100 mm/kasan/common.c:521 kasan_kmalloc include/linux/kasan.h:227 [inline] __kmalloc+0x13d/0x2c0 mm/slub.c:4436 kmalloc include/linux/slab.h:624 [inline] kzalloc include/linux/slab.h:750 [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:1922 [inline] __sys_connect+0x3cb/0x450 net/socket.c:1939 __do_sys_connect net/socket.c:1949 [inline] __se_sys_connect net/socket.c:1946 [inline] __x64_sys_connect+0x7a/0x90 net/socket.c:1946 x64_sys_call+0x7c/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:43 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 Freed by task 313: 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:365 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:373 kasan_slab_free include/linux/kasan.h:193 [inline] slab_free_hook mm/slub.c:1728 [inline] slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1754 slab_free mm/slub.c:3526 [inline] kfree+0xc4/0x270 mm/slub.c:4588 l2tp_session_free net/l2tp/l2tp_core.c:168 [inline] l2tp_session_put+0xaf/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+0x6c8/0xbb0 kernel/workqueue.c:2328 worker_thread+0xaa0/0x1250 kernel/workqueue.c:2475 kthread+0x3f5/0x4f0 kernel/kthread.c:337 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 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_common kernel/rcu/tree.c:3011 [inline] call_rcu+0x10b/0xf60 kernel/rcu/tree.c:3129 pppol2tp_release+0x1e3/0x2b0 net/l2tp/l2tp_ppp.c:447 __sock_release net/socket.c:649 [inline] sock_close+0xb8/0x200 net/socket.c:1335 __fput+0x22b/0x900 fs/file_table.c:311 ____fput+0x15/0x20 fs/file_table.c:339 task_work_run+0x127/0x190 kernel/task_work.c:188 exit_task_work include/linux/task_work.h:33 [inline] do_exit+0xb70/0x29a0 kernel/exit.c:890 __do_sys_exit kernel/exit.c:973 [inline] __se_sys_exit kernel/exit.c:971 [inline] __ia32_sys_exit+0x0/0x40 kernel/exit.c:971 x64_sys_call+0x44/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:61 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 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_common kernel/rcu/tree.c:3011 [inline] call_rcu+0x10b/0xf60 kernel/rcu/tree.c:3129 fib6_info_release include/net/ip6_fib.h:349 [inline] fib6_del_route net/ipv6/ip6_fib.c:1998 [inline] fib6_del+0xbf0/0xf00 net/ipv6/ip6_fib.c:2031 fib6_clean_node+0x2a1/0x540 net/ipv6/ip6_fib.c:2193 fib6_walk_continue+0x54b/0x740 net/ipv6/ip6_fib.c:2115 fib6_walk+0x153/0x290 net/ipv6/ip6_fib.c:2163 fib6_clean_tree net/ipv6/ip6_fib.c:2243 [inline] __fib6_clean_all net/ipv6/ip6_fib.c:2259 [inline] fib6_clean_all+0x1a1/0x270 net/ipv6/ip6_fib.c:2270 rt6_sync_down_dev net/ipv6/route.c:4906 [inline] rt6_disable_ip+0x115/0x730 net/ipv6/route.c:4911 addrconf_ifdown+0x144/0x1910 net/ipv6/addrconf.c:3799 addrconf_notify+0x3bd/0xe00 net/ipv6/addrconf.c:-1 notifier_call_chain kernel/notifier.c:83 [inline] raw_notifier_call_chain+0x90/0x100 kernel/notifier.c:391 call_netdevice_notifiers_info net/core/dev.c:2070 [inline] call_netdevice_notifiers_extack net/core/dev.c:2082 [inline] call_netdevice_notifiers net/core/dev.c:2096 [inline] dev_close_many+0x325/0x4d0 net/core/dev.c:1671 unregister_netdevice_many+0x477/0x1a00 net/core/dev.c:11152 xfrmi_exit_batch_net+0x20a/0x260 net/xfrm/xfrm_interface_core.c:766 ops_exit_list net/core/net_namespace.c:177 [inline] cleanup_net+0x605/0xae0 net/core/net_namespace.c:599 process_one_work+0x6c8/0xbb0 kernel/workqueue.c:2328 worker_thread+0xaa0/0x1250 kernel/workqueue.c:2475 kthread+0x3f5/0x4f0 kernel/kthread.c:337 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 The buggy address belongs to the object at ffff88812682c800 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 400 bytes inside of 512-byte region [ffff88812682c800, ffff88812682ca00) The buggy address belongs to the page: page:ffffea00049a0b00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x12682c head:ffffea00049a0b00 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x4000000000010200(slab|head|zone=1) raw: 4000000000010200 ffffea000501db00 0000000300000003 ffff888100042f00 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 2259, ts 120305914602, free_ts 118773369867 set_page_owner include/linux/page_owner.h:33 [inline] post_alloc_hook+0x192/0x1b0 mm/page_alloc.c:2607 prep_new_page+0x1c/0x110 mm/page_alloc.c:2613 get_page_from_freelist+0x2c3a/0x2cd0 mm/page_alloc.c:4487 __alloc_pages+0x1a2/0x460 mm/page_alloc.c:5824 alloc_slab_page mm/slub.c:-1 [inline] allocate_slab mm/slub.c:1937 [inline] new_slab+0xa0/0x4d0 mm/slub.c:2000 ___slab_alloc+0x3ac/0x840 mm/slub.c:3033 __slab_alloc+0x49/0x90 mm/slub.c:3120 slab_alloc_node mm/slub.c:3211 [inline] slab_alloc mm/slub.c:3255 [inline] kmem_cache_alloc_trace+0x146/0x270 mm/slub.c:3272 kmalloc include/linux/slab.h:619 [inline] kmalloc_array include/linux/slab.h:658 [inline] rtnl_newlink+0x17f/0x1900 net/core/rtnetlink.c:3571 rtnetlink_rcv_msg+0x9fd/0xcb0 net/core/rtnetlink.c:5653 netlink_rcv_skb+0x1e9/0x430 net/netlink/af_netlink.c:2511 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:5671 netlink_unicast_kernel net/netlink/af_netlink.c:1322 [inline] netlink_unicast+0x86c/0xa30 net/netlink/af_netlink.c:1348 netlink_sendmsg+0x879/0xb80 net/netlink/af_netlink.c:1922 sock_sendmsg_nosec net/socket.c:704 [inline] __sock_sendmsg net/socket.c:716 [inline] __sys_sendto+0x46d/0x620 net/socket.c:2062 __do_sys_sendto net/socket.c:2074 [inline] __se_sys_sendto net/socket.c:2070 [inline] __x64_sys_sendto+0xe5/0x100 net/socket.c:2070 page last free stack trace: reset_page_owner include/linux/page_owner.h:26 [inline] free_pages_prepare mm/page_alloc.c:1474 [inline] free_pcp_prepare mm/page_alloc.c:1546 [inline] free_unref_page_prepare+0x5fa/0x600 mm/page_alloc.c:3536 free_unref_page+0xae/0x540 mm/page_alloc.c:3618 free_the_page mm/page_alloc.c:805 [inline] __free_pages+0x6c/0x100 mm/page_alloc.c:5900 __vunmap+0x801/0x980 mm/vmalloc.c:2660 __vfree mm/vmalloc.c:2709 [inline] vfree+0x8b/0xc0 mm/vmalloc.c:2740 kcov_put kernel/kcov.c:417 [inline] kcov_close+0x2b/0x50 kernel/kcov.c:519 __fput+0x22b/0x900 fs/file_table.c:311 ____fput+0x15/0x20 fs/file_table.c:339 task_work_run+0x127/0x190 kernel/task_work.c:188 exit_task_work include/linux/task_work.h:33 [inline] do_exit+0xb70/0x29a0 kernel/exit.c:890 do_group_exit+0x149/0x310 kernel/exit.c:1004 get_signal+0x64f/0x1430 kernel/signal.c:2907 arch_do_signal_or_restart+0xe2/0x1100 arch/x86/kernel/signal.c:867 handle_signal_work kernel/entry/common.c:154 [inline] exit_to_user_mode_loop+0xa7/0xe0 kernel/entry/common.c:178 exit_to_user_mode_prepare+0x87/0xd0 kernel/entry/common.c:214 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline] syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:307 Memory state around the buggy address: ffff88812682c880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88812682c900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88812682c980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88812682ca00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88812682ca80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ==================================================================