================================================================== BUG: KASAN: use-after-free in hlist_unhashed include/linux/list.h:854 [inline] BUG: KASAN: use-after-free in hlist_del_init_rcu include/linux/rculist.h:183 [inline] BUG: KASAN: use-after-free in l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1230 [inline] BUG: KASAN: use-after-free in l2tp_tunnel_del_work+0xd8/0x410 net/l2tp/l2tp_core.c:1271 Read of size 8 at addr ffff8881437cec80 by task kworker/u4:34/9882 CPU: 0 PID: 9882 Comm: kworker/u4:34 Tainted: G W syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 Workqueue: l2tp l2tp_tunnel_del_work Call Trace: __dump_stack+0x21/0x24 lib/dump_stack.c:88 dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106 print_address_description+0x71/0x200 mm/kasan/report.c:316 print_report+0x4a/0x60 mm/kasan/report.c:420 kasan_report+0x122/0x150 mm/kasan/report.c:524 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:351 hlist_unhashed include/linux/list.h:854 [inline] hlist_del_init_rcu include/linux/rculist.h:183 [inline] l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1230 [inline] l2tp_tunnel_del_work+0xd8/0x410 net/l2tp/l2tp_core.c:1271 process_one_work+0x717/0xc30 kernel/workqueue.c:2302 worker_thread+0xa4d/0x11d0 kernel/workqueue.c:2449 kthread+0x281/0x320 kernel/kthread.c:386 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 Allocated by task 17967: kasan_save_stack mm/kasan/common.c:46 [inline] kasan_set_track+0x4b/0x70 mm/kasan/common.c:53 kasan_save_alloc_info+0x1f/0x30 mm/kasan/generic.c:505 ____kasan_kmalloc mm/kasan/common.c:380 [inline] __kasan_kmalloc+0x95/0xb0 mm/kasan/common.c:389 kasan_kmalloc include/linux/kasan.h:212 [inline] __do_kmalloc_node mm/slab_common.c:938 [inline] __kmalloc+0xb4/0x1e0 mm/slab_common.c:951 kmalloc include/linux/slab.h:568 [inline] kzalloc include/linux/slab.h:699 [inline] l2tp_session_create+0x38/0xbd0 net/l2tp/l2tp_core.c:1614 pppol2tp_connect+0xbf5/0x1640 net/l2tp/l2tp_ppp.c:771 __sys_connect_file net/socket.c:2001 [inline] __sys_connect+0x3da/0x460 net/socket.c:2018 __do_sys_connect net/socket.c:2028 [inline] __se_sys_connect net/socket.c:2025 [inline] __x64_sys_connect+0x7a/0x90 net/socket.c:2025 x64_sys_call+0x88d/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:43 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x68/0xd2 Freed by task 17967: kasan_save_stack mm/kasan/common.c:46 [inline] kasan_set_track+0x4b/0x70 mm/kasan/common.c:53 kasan_save_free_info+0x2b/0x40 mm/kasan/generic.c:516 ____kasan_slab_free+0x132/0x180 mm/kasan/common.c:242 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:250 kasan_slab_free include/linux/kasan.h:178 [inline] slab_free_hook mm/slub.c:1750 [inline] slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1776 slab_free mm/slub.c:3712 [inline] __kmem_cache_free+0xb7/0x1b0 mm/slub.c:3728 kfree+0x6f/0xf0 mm/slab_common.c:990 l2tp_session_free net/l2tp/l2tp_core.c:168 [inline] l2tp_session_put+0xaf/0x1a0 net/l2tp/l2tp_core.c:193 pppol2tp_ioctl+0x748/0x960 net/l2tp/l2tp_ppp.c:-1 pppox_ioctl+0x1f6/0x330 drivers/net/ppp/pppox.c:93 sock_do_ioctl+0x114/0x330 net/socket.c:1192 sock_ioctl+0x475/0x700 net/socket.c:1311 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl+0x12f/0x1b0 fs/ioctl.c:856 __x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:856 x64_sys_call+0x58b/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:17 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x68/0xd2 Last potentially related work creation: kasan_save_stack+0x3a/0x60 mm/kasan/common.c:46 __kasan_record_aux_stack+0xb6/0xc0 mm/kasan/generic.c:486 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:496 kvfree_call_rcu+0x8b/0x7a0 kernel/rcu/tree.c:3445 inet6_ifa_finish_destroy+0x129/0x1b0 net/ipv6/addrconf.c:1007 in6_ifa_put include/net/addrconf.h:459 [inline] addrconf_ifdown+0x1254/0x1950 net/ipv6/addrconf.c:3960 addrconf_notify+0x39f/0xe30 net/ipv6/addrconf.c:-1 notifier_call_chain kernel/notifier.c:87 [inline] raw_notifier_call_chain+0xa1/0x110 kernel/notifier.c:455 call_netdevice_notifiers_info net/core/dev.c:2022 [inline] call_netdevice_notifiers_extack net/core/dev.c:2060 [inline] call_netdevice_notifiers net/core/dev.c:2074 [inline] dev_close_many+0x325/0x4d0 net/core/dev.c:1622 unregister_netdevice_many+0x43f/0x1910 net/core/dev.c:10979 default_device_exit_batch+0x951/0x9f0 net/core/dev.c:11518 ops_exit_list net/core/net_namespace.c:177 [inline] cleanup_net+0x630/0xb10 net/core/net_namespace.c:604 process_one_work+0x717/0xc30 kernel/workqueue.c:2302 worker_thread+0xa4d/0x11d0 kernel/workqueue.c:2449 kthread+0x281/0x320 kernel/kthread.c:386 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 Second to last potentially related work creation: kasan_save_stack+0x3a/0x60 mm/kasan/common.c:46 __kasan_record_aux_stack+0xb6/0xc0 mm/kasan/generic.c:486 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:496 insert_work+0x51/0x300 kernel/workqueue.c:1368 __queue_work+0x9d0/0xd50 kernel/workqueue.c:1527 __queue_delayed_work+0x188/0x200 kernel/workqueue.c:1675 mod_delayed_work_on+0x74/0xe0 kernel/workqueue.c:1749 mod_delayed_work include/linux/workqueue.h:540 [inline] addrconf_mod_dad_work+0x7d/0x120 net/ipv6/addrconf.c:335 addrconf_dad_start+0x96/0xd0 net/ipv6/addrconf.c:4139 inet6_addr_add+0x650/0x9c0 net/ipv6/addrconf.c:3057 inet6_rtm_newaddr+0x74a/0xa10 net/ipv6/addrconf.c:4999 rtnetlink_rcv_msg+0xb28/0xde0 net/core/rtnetlink.c:6154 netlink_rcv_skb+0x200/0x450 net/netlink/af_netlink.c:2526 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:6172 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] netlink_unicast+0x8c1/0xa60 net/netlink/af_netlink.c:1345 netlink_sendmsg+0x8b9/0xbd0 net/netlink/af_netlink.c:1878 sock_sendmsg_nosec net/socket.c:716 [inline] __sock_sendmsg net/socket.c:728 [inline] __sys_sendto+0x4ac/0x660 net/socket.c:2143 __do_sys_sendto net/socket.c:2155 [inline] __se_sys_sendto net/socket.c:2151 [inline] __x64_sys_sendto+0xe5/0x100 net/socket.c:2151 x64_sys_call+0x83/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:45 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x68/0xd2 The buggy address belongs to the object at ffff8881437cec00 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 128 bytes inside of 512-byte region [ffff8881437cec00, ffff8881437cee00) The buggy address belongs to the physical page: page:ffffea00050df300 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1437cc head:ffffea00050df300 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x4000000000010200(slab|head|zone=1) raw: 4000000000010200 dead000000000100 dead000000000122 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 7775, tgid 7772 (syz.5.2340), ts 534019566573, free_ts 533921796014 set_page_owner include/linux/page_owner.h:33 [inline] post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2673 prep_new_page+0x1c/0x110 mm/page_alloc.c:2680 get_page_from_freelist+0x2ca9/0x2d20 mm/page_alloc.c:4587 __alloc_pages+0x1fa/0x610 mm/page_alloc.c:5931 alloc_slab_page+0x6e/0xf0 include/linux/gfp.h:-1 allocate_slab mm/slub.c:1967 [inline] new_slab+0x98/0x3e0 mm/slub.c:2020 ___slab_alloc+0x70f/0xb70 mm/slub.c:3177 __slab_alloc+0x5e/0xa0 mm/slub.c:3263 slab_alloc_node mm/slub.c:3348 [inline] __kmem_cache_alloc_node+0x204/0x2d0 mm/slub.c:3423 kmalloc_trace+0x29/0xb0 mm/slab_common.c:1028 kmalloc include/linux/slab.h:563 [inline] kzalloc include/linux/slab.h:699 [inline] ipv6_add_addr+0x411/0xe80 net/ipv6/addrconf.c:1119 add_addr+0x8a/0x290 net/ipv6/addrconf.c:3173 add_v4_addrs+0x659/0xb20 net/ipv6/addrconf.c:3235 addrconf_sit_config net/ipv6/addrconf.c:3486 [inline] addrconf_init_auto_addrs+0x3d6/0xbc0 net/ipv6/addrconf.c:3524 addrconf_notify+0x7fe/0xe30 net/ipv6/addrconf.c:3711 notifier_call_chain kernel/notifier.c:87 [inline] raw_notifier_call_chain+0xa1/0x110 kernel/notifier.c:455 page last free stack trace: reset_page_owner include/linux/page_owner.h:26 [inline] free_pages_prepare mm/page_alloc.c:1581 [inline] free_pcp_prepare mm/page_alloc.c:1655 [inline] free_unref_page_prepare+0x81b/0x820 mm/page_alloc.c:3622 free_unref_page+0x93/0x530 mm/page_alloc.c:3720 free_the_page mm/page_alloc.c:863 [inline] __free_pages+0x67/0x100 mm/page_alloc.c:6021 __free_slab+0xc7/0x1a0 mm/slub.c:2044 free_slab mm/slub.c:2059 [inline] discard_slab mm/slub.c:2065 [inline] __unfreeze_partials+0x15a/0x190 mm/slub.c:2614 put_cpu_partial+0xa9/0x100 mm/slub.c:2690 __slab_free+0x1c4/0x280 mm/slub.c:3589 do_slab_free mm/slub.c:3666 [inline] ___cache_free+0xbf/0xd0 mm/slub.c:3722 qlink_free mm/kasan/quarantine.c:168 [inline] qlist_free_all+0xc6/0x140 mm/kasan/quarantine.c:187 kasan_quarantine_reduce+0x14a/0x170 mm/kasan/quarantine.c:294 __kasan_slab_alloc+0x24/0x80 mm/kasan/common.c:311 kasan_slab_alloc include/linux/kasan.h:202 [inline] slab_post_alloc_hook+0x4f/0x2d0 mm/slab.h:768 slab_alloc_node mm/slub.c:3382 [inline] slab_alloc mm/slub.c:3392 [inline] __kmem_cache_alloc_lru mm/slub.c:3399 [inline] kmem_cache_alloc_lru+0x104/0x280 mm/slub.c:3415 alloc_inode_sb include/linux/fs.h:3263 [inline] shmem_alloc_inode+0x28/0x40 mm/shmem.c:3909 alloc_inode fs/inode.c:264 [inline] new_inode_pseudo+0x70/0x1f0 fs/inode.c:1074 new_inode+0x28/0x1e0 fs/inode.c:1102 Memory state around the buggy address: ffff8881437ceb80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff8881437cec00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff8881437cec80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8881437ced00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8881437ced80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================