================================================================== BUG: KASAN: use-after-free in pppol2tp_sock_to_session+0x1a0/0x1b0 net/l2tp/l2tp_ppp.c:156 Read of size 4 at addr ffff88810ab62400 by task syz.8.2365/8688 CPU: 0 PID: 8688 Comm: syz.8.2365 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/06/2026 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_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:308 pppol2tp_sock_to_session+0x1a0/0x1b0 net/l2tp/l2tp_ppp.c:156 pppol2tp_release+0x150/0x2b0 net/l2tp/l2tp_ppp.c:435 __sock_release net/socket.c:597 [inline] sock_close+0xb8/0x200 net/socket.c:1287 __fput+0x2dc/0x730 fs/file_table.c:281 ____fput+0x15/0x20 fs/file_table.c:314 task_work_run+0x127/0x190 kernel/task_work.c:189 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_user_mode_loop+0xcb/0xe0 kernel/entry/common.c:175 exit_to_user_mode_prepare+0x76/0xa0 kernel/entry/common.c:202 syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:277 do_syscall_64+0x3d/0x40 arch/x86/entry/common.c:56 entry_SYSCALL_64_after_hwframe+0x61/0xcb RIP: 0033:0x7f0cb31d44d9 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:00007fff71648108 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4 RAX: 0000000000000000 RBX: 00007fff716481f0 RCX: 00007f0cb31d44d9 RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003 RBP: 00000000000abdca R08: 0000000000000001 R09: 0000000000000000 R10: 0000001b33a20000 R11: 0000000000000246 R12: 00007fff71648230 R13: 00007f0cb3450fac R14: 00000000000abe31 R15: 00007f0cb3450fa0 Allocated by task 8689: 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 1435: 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 l2tp_session_delete+0x3a9/0x4a0 net/l2tp/l2tp_core.c:1589 l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1235 [inline] l2tp_tunnel_del_work+0x180/0x3d0 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 Last potentially related work creation: kasan_save_stack+0x3a/0x60 mm/kasan/common.c:38 __kasan_record_aux_stack+0xd2/0x100 mm/kasan/generic.c:348 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358 kvfree_call_rcu+0x117/0x670 kernel/rcu/tree.c:3539 drop_sysctl_table+0x2f5/0x430 fs/proc/proc_sysctl.c:1684 drop_sysctl_table+0x2e4/0x430 fs/proc/proc_sysctl.c:1687 unregister_sysctl_table+0x75/0x120 fs/proc/proc_sysctl.c:1722 unregister_net_sysctl_table+0x15/0x20 net/sysctl_net.c:127 __devinet_sysctl_unregister net/ipv4/devinet.c:2621 [inline] devinet_sysctl_unregister net/ipv4/devinet.c:2649 [inline] inetdev_destroy net/ipv4/devinet.c:326 [inline] inetdev_event+0x788/0x1010 net/ipv4/devinet.c:1612 notifier_call_chain kernel/notifier.c:83 [inline] raw_notifier_call_chain+0x90/0x100 kernel/notifier.c:410 call_netdevice_notifiers_info net/core/dev.c:2052 [inline] call_netdevice_notifiers_extack net/core/dev.c:2064 [inline] call_netdevice_notifiers net/core/dev.c:2078 [inline] unregister_netdevice_many+0x100e/0x19f0 net/core/dev.c:10779 default_device_exit_batch+0x35e/0x3c0 net/core/dev.c:11299 ops_exit_list net/core/net_namespace.c:190 [inline] cleanup_net+0x5fe/0xb80 net/core/net_namespace.c:609 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 Second to last potentially related work creation: kasan_save_stack+0x3a/0x60 mm/kasan/common.c:38 __kasan_record_aux_stack+0xd2/0x100 mm/kasan/generic.c:348 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358 __call_rcu kernel/rcu/tree.c:2980 [inline] call_rcu+0x11a/0x1090 kernel/rcu/tree.c:3054 inetdev_destroy net/ipv4/devinet.c:330 [inline] inetdev_event+0x825/0x1010 net/ipv4/devinet.c:1612 notifier_call_chain kernel/notifier.c:83 [inline] raw_notifier_call_chain+0x90/0x100 kernel/notifier.c:410 call_netdevice_notifiers_info net/core/dev.c:2052 [inline] call_netdevice_notifiers_extack net/core/dev.c:2064 [inline] call_netdevice_notifiers net/core/dev.c:2078 [inline] unregister_netdevice_many+0x100e/0x19f0 net/core/dev.c:10779 ip_tunnel_delete_nets+0x343/0x390 net/ipv4/ip_tunnel.c:1122 erspan_exit_batch_net+0x22/0x30 net/ipv4/ip_gre.c:1749 ops_exit_list net/core/net_namespace.c:190 [inline] cleanup_net+0x5fe/0xb80 net/core/net_namespace.c:609 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 The buggy address belongs to the object at ffff88810ab62400 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 0 bytes inside of 512-byte region [ffff88810ab62400, ffff88810ab62600) The buggy address belongs to the page: page:ffffea00042ad800 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10ab60 head:ffffea00042ad800 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x4000000000010200(slab|head) raw: 4000000000010200 dead000000000100 dead000000000122 ffff888100043080 raw: 0000000000000000 0000000080100010 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 1, ts 1847481719, free_ts 0 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] kmem_cache_alloc_trace+0x1a8/0x2e0 mm/slub.c:2977 kmem_cache_alloc_node_trace include/linux/slab.h:443 [inline] kmalloc_node include/linux/slab.h:573 [inline] kzalloc_node include/linux/slab.h:678 [inline] blkg_alloc+0x6d/0x570 block/blk-cgroup.c:158 blkcg_init_queue+0x2d/0x330 block/blk-cgroup.c:1171 blk_alloc_queue+0x444/0x5f0 block/blk-core.c:575 blk_mq_init_queue_data block/blk-mq.c:3171 [inline] blk_mq_init_queue+0x37/0xd0 block/blk-mq.c:3190 scsi_mq_alloc_queue+0x42/0x140 drivers/scsi/scsi_lib.c:1913 scsi_alloc_sdev+0x611/0x920 drivers/scsi/scsi_scan.c:284 scsi_probe_and_add_lun+0x17d/0x3370 drivers/scsi/scsi_scan.c:1098 __scsi_scan_target+0x1d2/0xbf0 drivers/scsi/scsi_scan.c:1581 scsi_scan_channel drivers/scsi/scsi_scan.c:1669 [inline] scsi_scan_host_selected+0x34e/0x600 drivers/scsi/scsi_scan.c:1698 page_owner free stack trace missing Memory state around the buggy address: ffff88810ab62300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88810ab62380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff88810ab62400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88810ab62480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88810ab62500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== ------------[ cut here ]------------ WARNING: CPU: 1 PID: 8688 at net/l2tp/l2tp_ppp.c:156 pppol2tp_sock_to_session+0x167/0x1b0 net/l2tp/l2tp_ppp.c:156 Modules linked in: CPU: 1 PID: 8688 Comm: syz.8.2365 Tainted: G B syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/06/2026 RIP: 0010:pppol2tp_sock_to_session+0x167/0x1b0 net/l2tp/l2tp_ppp.c:156 Code: 5d c3 e8 7c b3 34 fd be 02 00 00 00 eb 0a e8 70 b3 34 fd be 01 00 00 00 4c 89 f7 e8 f3 31 0e fe e9 0f ff ff ff e8 59 b3 34 fd <0f> 0b 48 89 df e8 ef 00 00 00 eb bd e8 48 b3 34 fd 4c 89 f7 be 03 RSP: 0018:ffffc90000d67d68 EFLAGS: 00010293 RAX: ffffffff843003c7 RBX: ffff8881270f9800 RCX: ffff888133172800 RDX: 0000000000000000 RSI: 000000000d377770 RDI: 000000000c04eb7d RBP: ffffc90000d67d88 R08: 0000000000000003 R09: 0000000000000004 R10: dffffc0000000000 R11: fffffbfff0dcfa48 R12: dffffc0000000000 R13: dffffc0000000000 R14: 000000000d377770 R15: ffff88810ab62400 FS: 0000555560d5f500(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f7891c99000 CR3: 00000001102a1000 CR4: 00000000003506a0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: pppol2tp_release+0x150/0x2b0 net/l2tp/l2tp_ppp.c:435 __sock_release net/socket.c:597 [inline] sock_close+0xb8/0x200 net/socket.c:1287 __fput+0x2dc/0x730 fs/file_table.c:281 ____fput+0x15/0x20 fs/file_table.c:314 task_work_run+0x127/0x190 kernel/task_work.c:189 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_user_mode_loop+0xcb/0xe0 kernel/entry/common.c:175 exit_to_user_mode_prepare+0x76/0xa0 kernel/entry/common.c:202 syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:277 do_syscall_64+0x3d/0x40 arch/x86/entry/common.c:56 entry_SYSCALL_64_after_hwframe+0x61/0xcb RIP: 0033:0x7f0cb31d44d9 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:00007fff71648108 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4 RAX: 0000000000000000 RBX: 00007fff716481f0 RCX: 00007f0cb31d44d9 RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003 RBP: 00000000000abdca R08: 0000000000000001 R09: 0000000000000000 R10: 0000001b33a20000 R11: 0000000000000246 R12: 00007fff71648230 R13: 00007f0cb3450fac R14: 00000000000abe31 R15: 00007f0cb3450fa0 ---[ end trace 2b18c8391b3a2bdf ]---