================================================================== BUG: KASAN: use-after-free in hlist_unhashed include/linux/list.h:826 [inline] BUG: KASAN: use-after-free in hlist_del_init include/linux/list.h:883 [inline] BUG: KASAN: use-after-free in l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1232 [inline] BUG: KASAN: use-after-free in l2tp_tunnel_del_work+0xcd/0x3d0 net/l2tp/l2tp_core.c:1273 Read of size 8 at addr ffff888128e06880 by task kworker/u4:3/313 CPU: 0 PID: 313 Comm: kworker/u4:3 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026 Workqueue: l2tp l2tp_tunnel_del_work 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 hlist_unhashed include/linux/list.h:826 [inline] hlist_del_init include/linux/list.h:883 [inline] l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1232 [inline] l2tp_tunnel_del_work+0xcd/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 Allocated by task 659: 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:1923 [inline] __sys_connect+0x3cb/0x450 net/socket.c:1940 __do_sys_connect net/socket.c:1950 [inline] __se_sys_connect net/socket.c:1947 [inline] __x64_sys_connect+0x7a/0x90 net/socket.c:1947 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 661: 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 pppol2tp_ioctl+0x748/0x960 net/l2tp/l2tp_ppp.c:-1 pppox_ioctl+0x1e4/0x320 drivers/net/ppp/pppox.c:93 sock_do_ioctl+0x103/0x310 net/socket.c:1138 sock_ioctl+0x459/0x6d0 net/socket.c:1257 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl+0x121/0x1a0 fs/ioctl.c:860 __x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:860 x64_sys_call+0x2f/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:17 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 The buggy address belongs to the object at ffff888128e06800 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 128 bytes inside of 512-byte region [ffff888128e06800, ffff888128e06a00) The buggy address belongs to the page: page:ffffea0004a38100 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x128e04 head:ffffea0004a38100 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 289, ts 24078068576, free_ts 0 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] __kmalloc+0x16a/0x2c0 mm/slub.c:4432 kmalloc include/linux/slab.h:624 [inline] kzalloc include/linux/slab.h:750 [inline] new_dir fs/proc/proc_sysctl.c:961 [inline] get_subdir fs/proc/proc_sysctl.c:1006 [inline] __register_sysctl_table+0xa35/0x1240 fs/proc/proc_sysctl.c:1355 register_net_sysctl+0x21d/0x230 net/sysctl_net.c:169 neigh_sysctl_register+0x9a9/0xa90 net/core/neighbour.c:3718 addrconf_sysctl_register+0xb3/0x1a0 net/ipv6/addrconf.c:7210 ipv6_add_dev+0xc09/0x1150 net/ipv6/addrconf.c:456 addrconf_notify+0x582/0xe00 net/ipv6/addrconf.c:3603 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+0x119/0x190 net/core/dev.c:2096 page_owner free stack trace missing Memory state around the buggy address: ffff888128e06780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888128e06800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff888128e06880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888128e06900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888128e06980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================