================================================================== BUG: KASAN: use-after-free in hlist_unhashed include/linux/list.h:808 [inline] BUG: KASAN: use-after-free in hlist_del_init include/linux/list.h:865 [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 ffff88812032f080 by task kworker/u4:1/9 CPU: 1 PID: 9 Comm: kworker/u4:1 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:77 dump_stack_lvl+0x1a7/0x208 lib/dump_stack.c:118 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248 __kasan_report mm/kasan/report.c:435 [inline] kasan_report+0x100/0x140 mm/kasan/report.c:452 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:309 hlist_unhashed include/linux/list.h:808 [inline] hlist_del_init include/linux/list.h:865 [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+0x6fd/0xbc0 kernel/workqueue.c:2301 worker_thread+0xa8e/0x13c0 kernel/workqueue.c:2447 kthread+0x324/0x3b0 kernel/kthread.c:313 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298 Allocated by task 4155: 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:430 [inline] ____kasan_kmalloc mm/kasan/common.c:509 [inline] __kasan_kmalloc+0xd4/0x100 mm/kasan/common.c:518 kasan_kmalloc include/linux/kasan.h:254 [inline] __kmalloc+0x19f/0x330 mm/slub.c:4038 kmalloc include/linux/slab.h:560 [inline] kzalloc include/linux/slab.h:667 [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:1867 [inline] __sys_connect+0x3ce/0x450 net/socket.c:1884 __do_sys_connect net/socket.c:1894 [inline] __se_sys_connect net/socket.c:1891 [inline] __x64_sys_connect+0x7a/0x90 net/socket.c:1891 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x61/0xcb Freed by task 4155: 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:362 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:370 kasan_slab_free include/linux/kasan.h:220 [inline] slab_free_hook mm/slub.c:1600 [inline] slab_free_freelist_hook+0xc5/0x190 mm/slub.c:1626 slab_free mm/slub.c:3208 [inline] kfree+0xc0/0x270 mm/slub.c:4196 l2tp_session_free net/l2tp/l2tp_core.c:168 [inline] l2tp_session_put+0xb2/0x1a0 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+0xda/0x380 net/socket.c:1068 sock_ioctl+0x472/0x740 net/socket.c:1208 vfs_ioctl fs/ioctl.c:48 [inline] __do_sys_ioctl fs/ioctl.c:753 [inline] __se_sys_ioctl+0x121/0x1a0 fs/ioctl.c:739 __x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:739 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x61/0xcb The buggy address belongs to the object at ffff88812032f000 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 128 bytes inside of 512-byte region [ffff88812032f000, ffff88812032f200) The buggy address belongs to the page: page:ffffea000480cb00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x12032c head:ffffea000480cb00 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x4000000000010200(slab|head) raw: 4000000000010200 dead000000000100 dead000000000122 ffff888100043080 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 0x1d60c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_RETRY_MAYFAIL|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 4156, ts 170675355221, free_ts 170659929565 set_page_owner include/linux/page_owner.h:35 [inline] post_alloc_hook mm/page_alloc.c:2456 [inline] prep_new_page+0x176/0x190 mm/page_alloc.c:2462 get_page_from_freelist+0x225f/0x23f0 mm/page_alloc.c:4254 __alloc_pages_nodemask+0x29a/0x640 mm/page_alloc.c:5384 alloc_slab_page mm/slub.c:-1 [inline] allocate_slab mm/slub.c:1813 [inline] new_slab+0x84/0x3f0 mm/slub.c:1874 new_slab_objects mm/slub.c:2632 [inline] ___slab_alloc+0x2f8/0x4c0 mm/slub.c:2796 __slab_alloc+0x63/0xa0 mm/slub.c:2836 slab_alloc_node mm/slub.c:2918 [inline] slab_alloc mm/slub.c:2960 [inline] __kmalloc+0x1f9/0x330 mm/slub.c:4034 __kmalloc_node include/linux/slab.h:421 [inline] kmalloc_node include/linux/slab.h:578 [inline] kvmalloc_node+0x88/0x130 mm/util.c:612 kvmalloc include/linux/mm.h:833 [inline] kvzalloc include/linux/mm.h:841 [inline] netif_alloc_netdev_queues net/core/dev.c:9922 [inline] alloc_netdev_mqs+0x60d/0xca0 net/core/dev.c:10588 ip6gre_init_net+0xff/0x340 net/ipv6/ip6_gre.c:1617 ops_init+0x2c0/0x470 net/core/net_namespace.c:144 setup_net+0x34f/0xae0 net/core/net_namespace.c:345 copy_net_ns+0x314/0x520 net/core/net_namespace.c:486 create_new_namespaces+0x3a8/0x650 kernel/nsproxy.c:110 unshare_nsproxy_namespaces+0x120/0x170 kernel/nsproxy.c:231 ksys_unshare+0x4fa/0x820 kernel/fork.c:3156 page last free stack trace: reset_page_owner include/linux/page_owner.h:28 [inline] free_pages_prepare mm/page_alloc.c:1349 [inline] __free_pages_ok+0x80b/0x830 mm/page_alloc.c:1629 free_the_page mm/page_alloc.c:5445 [inline] __free_pages+0xd8/0x390 mm/page_alloc.c:5454 __free_slab+0xcf/0x190 mm/slub.c:1899 free_slab mm/slub.c:1914 [inline] discard_slab mm/slub.c:1920 [inline] unfreeze_partials+0x150/0x180 mm/slub.c:2415 put_cpu_partial+0xc1/0x180 mm/slub.c:2451 __slab_free+0x2c9/0x3a0 mm/slub.c:3100 do_slab_free mm/slub.c:3196 [inline] ___cache_free+0x10e/0x130 mm/slub.c:3215 qlink_free+0x50/0x90 mm/kasan/quarantine.c:157 qlist_free_all+0x5f/0xb0 mm/kasan/quarantine.c:176 kasan_quarantine_reduce+0x14a/0x160 mm/kasan/quarantine.c:283 __kasan_slab_alloc+0x2f/0xe0 mm/kasan/common.c:440 kasan_slab_alloc include/linux/kasan.h:244 [inline] slab_post_alloc_hook+0x5d/0x2f0 mm/slab.h:580 slab_alloc_node mm/slub.c:2952 [inline] slab_alloc mm/slub.c:2960 [inline] __kmalloc_track_caller+0x176/0x310 mm/slub.c:4541 kvasprintf+0xe3/0x1a0 lib/kasprintf.c:25 kvasprintf_const+0xf2/0x240 lib/kasprintf.c:49 kobject_set_name_vargs+0x61/0x110 lib/kobject.c:297 Memory state around the buggy address: ffff88812032ef80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88812032f000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88812032f080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88812032f100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88812032f180: fb fb fb 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