==================================================================
BUG: KASAN: use-after-free in pppol2tp_sock_to_session+0x1a0/0x1b0 net/l2tp/l2tp_ppp.c:156
Read of size 4 at addr ffff888120074400 by task syz.8.568/2664

CPU: 1 PID: 2664 Comm: syz.8.568 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/06/2026
Call Trace:
 <TASK>
 __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_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: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:184
 exit_to_user_mode_prepare+0x87/0xd0 kernel/entry/common.c:217
 __syscall_exit_to_user_mode_work kernel/entry/common.c:299 [inline]
 syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:310
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f5e5b162b19
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:00007fff842913b8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007fff842914a0 RCX: 00007f5e5b162b19
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 000000000002ee92 R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b2f520000 R11: 0000000000000246 R12: 00007fff842914e0
R13: 00007f5e5b3e8fac R14: 000000000002ef79 R15: 00007f5e5b3e8fa0
 </TASK>

Allocated by task 2665:
 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 312:
 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
 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+0x6c8/0xbb0 kernel/workqueue.c:2328
 worker_thread+0xaa0/0x1250 kernel/workqueue.c:2475
 kthread+0x3f5/0x4f0 kernel/kthread.c:337
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

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
 insert_work+0x51/0x310 kernel/workqueue.c:1373
 __queue_work+0x8e1/0xc60 kernel/workqueue.c:1539
 queue_work_on+0xde/0x150 kernel/workqueue.c:1566
 queue_work include/linux/workqueue.h:510 [inline]
 schedule_work include/linux/workqueue.h:571 [inline]
 __bpf_map_put kernel/bpf/syscall.c:502 [inline]
 bpf_map_put+0x1cf/0x240 kernel/bpf/syscall.c:508
 __bpf_free_used_maps kernel/bpf/core.c:2255 [inline]
 bpf_free_used_maps kernel/bpf/core.c:2261 [inline]
 bpf_prog_free_deferred+0x135/0x6d0 kernel/bpf/core.c:2293
 process_one_work+0x6c8/0xbb0 kernel/workqueue.c:2328
 worker_thread+0xaa0/0x1250 kernel/workqueue.c:2475
 kthread+0x3f5/0x4f0 kernel/kthread.c:337
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

The buggy address belongs to the object at ffff888120074400
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 0 bytes inside of
 512-byte region [ffff888120074400, ffff888120074600)
The buggy address belongs to the page:
page:ffffea0004801d00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x120074
head:ffffea0004801d00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 ffffea0004c85f00 0000000300000003 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 492, ts 33676388183, free_ts 27702351763
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x192/0x1b0 mm/page_alloc.c:2610
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2616
 get_page_from_freelist+0x2d42/0x2dd0 mm/page_alloc.c:4492
 __alloc_pages+0x1a2/0x460 mm/page_alloc.c:5829
 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_node include/linux/slab.h:487 [inline]
 kmalloc_node include/linux/slab.h:642 [inline]
 __bpf_map_area_alloc kernel/bpf/syscall.c:322 [inline]
 bpf_map_area_alloc+0x49/0xe0 kernel/bpf/syscall.c:335
 array_map_alloc+0x27a/0x6c0 kernel/bpf/arraymap.c:142
 find_and_alloc_map kernel/bpf/syscall.c:129 [inline]
 map_create+0x3f4/0x1fa0 kernel/bpf/syscall.c:860
 __sys_bpf+0x2ff/0x7d0 kernel/bpf/syscall.c:4615
 __do_sys_bpf kernel/bpf/syscall.c:4737 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:4735 [inline]
 __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:4735
 x64_sys_call+0x4b9/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:322
 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
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1477 [inline]
 free_pcp_prepare mm/page_alloc.c:1549 [inline]
 free_unref_page_prepare+0x5fa/0x600 mm/page_alloc.c:3540
 free_unref_page_list+0x138/0x9e0 mm/page_alloc.c:3677
 release_pages+0x1264/0x12c0 mm/swap.c:1033
 __pagevec_release+0x71/0xe0 mm/swap.c:1053
 pagevec_release include/linux/pagevec.h:81 [inline]
 shmem_undo_range+0x564/0x13b0 mm/shmem.c:965
 shmem_truncate_range mm/shmem.c:1064 [inline]
 shmem_evict_inode+0x1dc/0x970 mm/shmem.c:1146
 evict+0x4b6/0x8b0 fs/inode.c:650
 iput_final fs/inode.c:1779 [inline]
 iput+0x651/0x7e0 fs/inode.c:1805
 dentry_unlink_inode+0x338/0x3e0 fs/dcache.c:380
 __dentry_kill+0x45b/0x660 fs/dcache.c:586
 dentry_kill+0xc0/0x2a0 fs/dcache.c:-1
 dput+0x47/0x90 fs/dcache.c:893
 __fput+0x5c7/0x900 fs/file_table.c:319
 ____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:184

Memory state around the buggy address:
 ffff888120074300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888120074380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888120074400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff888120074480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888120074500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
------------[ cut here ]------------
WARNING: CPU: 0 PID: 2664 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: 2664 Comm: syz.8.568 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 ec 16 0a fd be 02 00 00 00 eb 0a e8 e0 16 0a fd be 01 00 00 00 4c 89 f7 e8 b3 bc f0 fd e9 0f ff ff ff e8 c9 16 0a fd <0f> 0b 48 89 df e8 ef 00 00 00 eb bd e8 b8 16 0a fd 4c 89 f7 be 03
RSP: 0018:ffffc90000a67d10 EFLAGS: 00010293
RAX: ffffffff845fc037 RBX: ffff88810bd58000 RCX: ffff88811b5c2800
RDX: 0000000000000000 RSI: 00000000053dcae0 RDI: 000000000c04eb7d
RBP: ffffc90000a67d30 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff0e1904c R12: dffffc0000000000
R13: dffffc0000000000 R14: 00000000053dcae0 R15: ffff888120074400
FS:  0000555574bfe500(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8840568c80 CR3: 0000000131ad4000 CR4: 00000000003506a0
Call Trace:
 <TASK>
 pppol2tp_release+0x150/0x2b0 net/l2tp/l2tp_ppp.c:435
 __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:184
 exit_to_user_mode_prepare+0x87/0xd0 kernel/entry/common.c:217
 __syscall_exit_to_user_mode_work kernel/entry/common.c:299 [inline]
 syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:310
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f5e5b162b19
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:00007fff842913b8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007fff842914a0 RCX: 00007f5e5b162b19
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 000000000002ee92 R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b2f520000 R11: 0000000000000246 R12: 00007fff842914e0
R13: 00007f5e5b3e8fac R14: 000000000002ef79 R15: 00007f5e5b3e8fa0
 </TASK>
---[ end trace 95a8243ea13a8582 ]---