================================================================== BUG: KASAN: use-after-free in __hlist_del include/linux/list.h:858 [inline] BUG: KASAN: use-after-free in hlist_del_init include/linux/list.h:884 [inline] BUG: KASAN: use-after-free in l2tp_session_unhash net/l2tp/l2tp_core.c:1202 [inline] BUG: KASAN: use-after-free in l2tp_session_delete+0x133/0x4a0 net/l2tp/l2tp_core.c:1584 Write of size 8 at addr ffff888134929480 by task syz.2.2623/9413 CPU: 0 PID: 9413 Comm: syz.2.2623 Tainted: G W syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 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_store8_noabort+0x17/0x20 mm/kasan/report_generic.c:314 __hlist_del include/linux/list.h:858 [inline] hlist_del_init include/linux/list.h:884 [inline] l2tp_session_unhash net/l2tp/l2tp_core.c:1202 [inline] l2tp_session_delete+0x133/0x4a0 net/l2tp/l2tp_core.c:1584 pppol2tp_release+0x169/0x2b0 net/l2tp/l2tp_ppp.c:439 __sock_release net/socket.c:649 [inline] sock_close+0xb8/0x200 net/socket.c:1336 __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 tracehook_notify_resume include/linux/tracehook.h:189 [inline] exit_to_user_mode_loop+0xd0/0xe0 kernel/entry/common.c:181 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 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86 entry_SYSCALL_64_after_hwframe+0x66/0xd0 RIP: 0033:0x7f16f901c159 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f16f78e9028 EFLAGS: 00000246 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 00007f16f92a4ae0 RCX: 00007f16f901c159 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005 RBP: 00007f16f90b3024 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f16f92a4b78 R14: 00007f16f92a4ae0 R15: 00007fffc9e36128 Allocated by task 9401: 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 9406: 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 ffff888134929400 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 128 bytes inside of 512-byte region [ffff888134929400, ffff888134929600) The buggy address belongs to the page: page:ffffea0004d24a00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x134928 head:ffffea0004d24a00 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 391, ts 28277547877, 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] alloc_workqueue+0x15e/0x1320 kernel/workqueue.c:4362 wg_newlink+0x355/0x7a0 drivers/net/wireguard/device.c:321 __rtnl_newlink net/core/rtnetlink.c:3536 [inline] rtnl_newlink+0x137f/0x1900 net/core/rtnetlink.c:3584 rtnetlink_rcv_msg+0x9fd/0xcb0 net/core/rtnetlink.c:5662 netlink_rcv_skb+0x1e9/0x430 net/netlink/af_netlink.c:2520 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:5680 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] netlink_unicast+0x86c/0xa30 net/netlink/af_netlink.c:1344 netlink_sendmsg+0x879/0xb80 net/netlink/af_netlink.c:1923 page_owner free stack trace missing Memory state around the buggy address: ffff888134929380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888134929400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff888134929480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888134929500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888134929580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================