==================================================================
BUG: KASAN: use-after-free in pppol2tp_sock_to_session+0x1a0/0x1b0 net/l2tp/l2tp_ppp.c:156
Read of size 4 at addr ffff8881002f3400 by task syz-executor274/310

CPU: 0 PID: 310 Comm: syz-executor274 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
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
 exit_task_work include/linux/task_work.h:33 [inline]
 do_exit+0xa7c/0x24e0 kernel/exit.c:879
 __do_sys_exit kernel/exit.c:962 [inline]
 __se_sys_exit kernel/exit.c:960 [inline]
 __x64_sys_exit+0x40/0x40 kernel/exit.c:960
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7fd68d073d79
Code: Unable to access opcode bytes at RIP 0x7fd68d073d4f.
RSP: 002b:00007ffc4c17bb08 EFLAGS: 00000246 ORIG_RAX: 000000000000003c
RAX: ffffffffffffffda RBX: 0000200000000040 RCX: 00007fd68d073d79
RDX: 00007fd68d085557 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000023800000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffc4c17bd28
R13: 0000000000000002 R14: 00007fd68d104ca0 R15: 0000000000000002

Allocated by task 309:
 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 112:
 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

The buggy address belongs to the object at ffff8881002f3400
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 0 bytes inside of
 512-byte region [ffff8881002f3400, ffff8881002f3600)
The buggy address belongs to the page:
page:ffffea000400bc00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1002f0
head:ffffea000400bc00 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 0, migratetype Unmovable, gfp_mask 0x0(), pid 1, ts 1117754180, free_ts 0
 create_dummy_stack mm/page_owner.c:65 [inline]
 register_early_stack+0x95/0xf0 mm/page_owner.c:81
 init_page_owner+0x32/0x800 mm/page_owner.c:91
 invoke_init_callbacks mm/page_ext.c:111 [inline]
 page_ext_init+0x3c1/0x407 mm/page_ext.c:416
 kernel_init_freeable+0x287/0x3c3 init/main.c:1483
page_owner free stack trace missing

Memory state around the buggy address:
 ffff8881002f3300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8881002f3380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8881002f3400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff8881002f3480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881002f3500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
------------[ cut here ]------------
WARNING: CPU: 1 PID: 310 at net/l2tp/l2tp_ppp.c:156 pppol2tp_sock_to_session+0x167/0x1b0 net/l2tp/l2tp_ppp.c:156
Modules linked in:
CPU: 0 PID: 310 Comm: syz-executor274 Tainted: G    B             syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
RIP: 0010:pppol2tp_sock_to_session+0x167/0x1b0 net/l2tp/l2tp_ppp.c:156
Code: 5d c3 e8 fc 61 35 fd be 02 00 00 00 eb 0a e8 f0 61 35 fd be 01 00 00 00 4c 89 f7 e8 e3 cf 0e fe e9 0f ff ff ff e8 d9 61 35 fd <0f> 0b 48 89 df e8 ef 00 00 00 eb bd e8 c8 61 35 fd 4c 89 f7 be 03
RSP: 0018:ffffc90000ad7c40 EFLAGS: 00010293
RAX: ffffffff842f5337 RBX: ffff88811edfd000 RCX: ffff88811f27e400
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000c04eb7d
RBP: ffffc90000ad7c60 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff0dcf848 R12: dffffc0000000000
R13: dffffc0000000000 R14: 0000000000000000 R15: ffff8881002f3400
FS:  0000000000000000(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd68d0854f0 CR3: 000000010cf85000 CR4: 00000000003506b0
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
 exit_task_work include/linux/task_work.h:33 [inline]
 do_exit+0xa7c/0x24e0 kernel/exit.c:879
 __do_sys_exit kernel/exit.c:962 [inline]
 __se_sys_exit kernel/exit.c:960 [inline]
 __x64_sys_exit+0x40/0x40 kernel/exit.c:960
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7fd68d073d79
Code: Unable to access opcode bytes at RIP 0x7fd68d073d4f.
RSP: 002b:00007ffc4c17bb08 EFLAGS: 00000246 ORIG_RAX: 000000000000003c
RAX: ffffffffffffffda RBX: 0000200000000040 RCX: 00007fd68d073d79
RDX: 00007fd68d085557 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000023800000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffc4c17bd28
R13: 0000000000000002 R14: 00007fd68d104ca0 R15: 0000000000000002