================================================================== 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:1225 [inline] BUG: KASAN: use-after-free in l2tp_tunnel_del_work+0xd8/0x410 net/l2tp/l2tp_core.c:1266 Read of size 8 at addr ffff88811e8ca480 by task kworker/u4:5/325 CPU: 0 PID: 325 Comm: kworker/u4:5 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/25/2026 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:1225 [inline] l2tp_tunnel_del_work+0xd8/0x410 net/l2tp/l2tp_core.c:1266 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 5023: 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:1609 pppol2tp_connect+0xbf5/0x1640 net/l2tp/l2tp_ppp.c:771 __sys_connect_file net/socket.c:2000 [inline] __sys_connect+0x3da/0x460 net/socket.c:2017 __do_sys_connect net/socket.c:2027 [inline] __se_sys_connect net/socket.c:2024 [inline] __x64_sys_connect+0x7a/0x90 net/socket.c:2024 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 5023: 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:1191 sock_ioctl+0x475/0x700 net/socket.c:1310 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 The buggy address belongs to the object at ffff88811e8ca400 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 128 bytes inside of 512-byte region [ffff88811e8ca400, ffff88811e8ca600) The buggy address belongs to the physical page: page:ffffea00047a3200 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x11e8c8 head:ffffea00047a3200 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x4000000000010200(slab|head|zone=1) raw: 4000000000010200 0000000000000000 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 5023, tgid 5022 (syz.0.1359), ts 278652180970, free_ts 275801738612 set_page_owner include/linux/page_owner.h:33 [inline] post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2672 prep_new_page+0x1c/0x110 mm/page_alloc.c:2679 get_page_from_freelist+0x2ca9/0x2d20 mm/page_alloc.c:4586 __alloc_pages+0x1fa/0x610 mm/page_alloc.c:5930 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] l2tp_tunnel_create+0x97/0x430 net/l2tp/l2tp_core.c:1421 pppol2tp_tunnel_get net/l2tp/l2tp_ppp.c:670 [inline] pppol2tp_connect+0x7ef/0x1640 net/l2tp/l2tp_ppp.c:727 __sys_connect_file net/socket.c:2000 [inline] __sys_connect+0x3da/0x460 net/socket.c:2017 __do_sys_connect net/socket.c:2027 [inline] __se_sys_connect net/socket.c:2024 [inline] __x64_sys_connect+0x7a/0x90 net/socket.c:2024 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 page last free stack trace: reset_page_owner include/linux/page_owner.h:26 [inline] free_pages_prepare mm/page_alloc.c:1580 [inline] free_pcp_prepare mm/page_alloc.c:1654 [inline] free_unref_page_prepare+0x80c/0x820 mm/page_alloc.c:3621 free_unref_page+0x93/0x530 mm/page_alloc.c:3719 free_the_page mm/page_alloc.c:863 [inline] __free_pages+0x67/0x100 mm/page_alloc.c:6020 __vunmap+0xa3c/0xc00 mm/vmalloc.c:2739 __vfree mm/vmalloc.c:2788 [inline] vfree+0x61/0x90 mm/vmalloc.c:2819 htable_put+0x5fb/0x650 net/netfilter/xt_hashlimit.c:432 hashlimit_mt_destroy+0x5c/0x70 net/netfilter/xt_hashlimit.c:977 cleanup_match net/ipv6/netfilter/ip6_tables.c:479 [inline] cleanup_entry+0x165/0x370 net/ipv6/netfilter/ip6_tables.c:663 translate_table+0x1e17/0x2030 net/ipv6/netfilter/ip6_tables.c:746 do_replace net/ipv6/netfilter/ip6_tables.c:1156 [inline] do_ip6t_set_ctl+0x9e9/0xe00 net/ipv6/netfilter/ip6_tables.c:1646 nf_setsockopt+0x284/0x2b0 net/netfilter/nf_sockopt.c:101 ipv6_setsockopt+0x170/0x1a0 net/ipv6/ipv6_sockglue.c:1030 rawv6_setsockopt+0x29e/0x660 net/ipv6/raw.c:1052 sock_common_setsockopt+0xb1/0xc0 net/core/sock.c:3707 __sys_setsockopt+0x2ff/0x4e0 net/socket.c:2277 __do_sys_setsockopt net/socket.c:2288 [inline] __se_sys_setsockopt net/socket.c:2285 [inline] __x64_sys_setsockopt+0xbf/0xd0 net/socket.c:2285 Memory state around the buggy address: ffff88811e8ca380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88811e8ca400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88811e8ca480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88811e8ca500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88811e8ca580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== device bridge_slave_1 left promiscuous mode bridge0: port 2(bridge_slave_1) entered disabled state device bridge_slave_0 left promiscuous mode bridge0: port 1(bridge_slave_0) entered disabled state device veth1_macvtap left promiscuous mode device veth0_vlan left promiscuous mode device bridge_slave_1 left promiscuous mode bridge0: port 2(bridge_slave_1) entered disabled state device bridge_slave_0 left promiscuous mode bridge0: port 1(bridge_slave_0) entered disabled state device bridge_slave_1 left promiscuous mode bridge0: port 2(bridge_slave_1) entered disabled state device bridge_slave_0 left promiscuous mode bridge0: port 1(bridge_slave_0) entered disabled state device bridge_slave_1 left promiscuous mode bridge0: port 2(bridge_slave_1) entered disabled state device bridge_slave_0 left promiscuous mode bridge0: port 1(bridge_slave_0) entered disabled state device veth1_macvtap left promiscuous mode device veth0_vlan left promiscuous mode device veth1_macvtap left promiscuous mode device veth0_vlan left promiscuous mode device veth1_macvtap left promiscuous mode device veth0_vlan left promiscuous mode