==================================================================
BUG: KASAN: use-after-free in pppol2tp_sock_to_session+0x1a0/0x1b0 net/l2tp/l2tp_ppp.c:156
Read of size 4 at addr ffff88810b2c3800 by task syz-executor172/298

CPU: 1 PID: 298 Comm: syz-executor172 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/08/2026
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: 0033:0x7f70b8dfcd79
Code: Unable to access opcode bytes at RIP 0x7f70b8dfcd4f.
RSP: 002b:00007ffe600f65f8 EFLAGS: 00000246 ORIG_RAX: 000000000000003c
RAX: ffffffffffffffda RBX: 0000200000000040 RCX: 00007f70b8dfcd79
RDX: 00007f70b8e0e557 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000023800000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffe600f6818
R13: 0000000000000002 R14: 00007f70b8e8dca0 R15: 0000000000000002

Allocated by task 297:
 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 49:
 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
 __call_rcu kernel/rcu/tree.c:2980 [inline]
 call_rcu+0x11a/0x1090 kernel/rcu/tree.c:3054
 blkg_release+0x23/0x30 block/blk-cgroup.c:114
 percpu_ref_put_many include/linux/percpu-refcount.h:322 [inline]
 percpu_ref_put include/linux/percpu-refcount.h:338 [inline]
 percpu_ref_call_confirm_rcu lib/percpu-refcount.c:163 [inline]
 percpu_ref_switch_to_atomic_rcu+0x5a3/0x5b0 lib/percpu-refcount.c:200
 rcu_do_batch+0x488/0xaf0 kernel/rcu/tree.c:2494
 rcu_core+0x50a/0xca0 kernel/rcu/tree.c:2735
 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2748
 __do_softirq+0x255/0x563 kernel/softirq.c:309

The buggy address belongs to the object at ffff88810b2c3800
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 0 bytes inside of
 512-byte region [ffff88810b2c3800, ffff88810b2c3a00)
The buggy address belongs to the page:
page:ffffea00042cb000 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10b2c0
head:ffffea00042cb000 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 ffffea00042c6300 0000000400000004 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 2724791416, 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:1911
 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:
 ffff88810b2c3700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88810b2c3780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88810b2c3800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff88810b2c3880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88810b2c3900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
------------[ cut here ]------------
WARNING: CPU: 1 PID: 298 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: 298 Comm: syz-executor172 Tainted: G    B             syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/08/2026
RIP: 0010:pppol2tp_sock_to_session+0x167/0x1b0 net/l2tp/l2tp_ppp.c:156
Code: 5d c3 e8 2c 5a 35 fd be 02 00 00 00 eb 0a e8 20 5a 35 fd be 01 00 00 00 4c 89 f7 e8 63 ca 0e fe e9 0f ff ff ff e8 09 5a 35 fd <0f> 0b 48 89 df e8 ef 00 00 00 eb bd e8 f8 59 35 fd 4c 89 f7 be 03
RSP: 0018:ffffc90000b97c40 EFLAGS: 00010293

RAX: ffffffff842f5aa7 RBX: ffff88811dcc5800 RCX: ffff88811edc1400
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000c04eb7d
RBP: ffffc90000b97c60 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff0dcf848 R12: dffffc0000000000
R13: dffffc0000000000 R14: 0000000000000000 R15: ffff88810b2c3800
FS:  0000000000000000(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f70b8e0e4f0 CR3: 000000000640f000 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
 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: 0033:0x7f70b8dfcd79
Code: Unable to access opcode bytes at RIP 0x7f70b8dfcd4f.
RSP: 002b:00007ffe600f65f8 EFLAGS: 00000246 ORIG_RAX: 000000000000003c
RAX: ffffffffffffffda RBX: 0000200000000040 RCX: 00007f70b8dfcd79
RDX: 00007f70b8