==================================================================
BUG: KASAN: use-after-free in pppol2tp_sock_to_session+0x1a0/0x1b0 net/l2tp/l2tp_ppp.c:156
Read of size 4 at addr ffff88812c460800 by task syz.0.1324/5251
CPU: 0 PID: 5251 Comm: syz.0.1324 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
__dump_stack+0x21/0x24 lib/dump_stack.c:88
dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
print_address_description+0x71/0x200 mm/kasan/report.c:316
print_report+0x4a/0x60 mm/kasan/report.c:420
kasan_report+0x122/0x150 mm/kasan/report.c:524
__asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:350
pppol2tp_sock_to_session+0x1a0/0x1b0 net/l2tp/l2tp_ppp.c:156
pppol2tp_release+0x150/0x2b0 net/l2tp/l2tp_ppp.c:434
__sock_release net/socket.c:652 [inline]
sock_close+0xc9/0x220 net/socket.c:1389
__fput+0x1fd/0x8f0 fs/file_table.c:320
____fput+0x15/0x20 fs/file_table.c:348
task_work_run+0x1e1/0x250 kernel/task_work.c:203
exit_task_work include/linux/task_work.h:39 [inline]
do_exit+0xa7c/0x27c0 kernel/exit.c:886
__do_sys_exit kernel/exit.c:995 [inline]
__se_sys_exit kernel/exit.c:993 [inline]
__x64_sys_exit+0x40/0x40 kernel/exit.c:993
x64_sys_call+0x67/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:61
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fd34119ce59
Code: Unable to access opcode bytes at 0x7fd34119ce2f.
RSP: 002b:00007fd341fd8fd8 EFLAGS: 00000246 ORIG_RAX: 000000000000003c
RAX: ffffffffffffffda RBX: 00007fd341415fa0 RCX: 00007fd34119ce59
RDX: 00007fd341fd99c8 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007fd341232d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd341416038 R14: 00007fd341415fa0 R15: 00007fff96bde3b8
Allocated by task 5248:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
kasan_save_alloc_info+0x1f/0x30 mm/kasan/generic.c:505
____kasan_kmalloc mm/kasan/common.c:380 [inline]
__kasan_kmalloc+0x95/0xb0 mm/kasan/common.c:389
kasan_kmalloc include/linux/kasan.h:212 [inline]
__do_kmalloc_node mm/slab_common.c:938 [inline]
__kmalloc+0xb4/0x1e0 mm/slab_common.c:951
kmalloc include/linux/slab.h:568 [inline]
kzalloc include/linux/slab.h:699 [inline]
l2tp_session_create+0x38/0xbd0 net/l2tp/l2tp_core.c:1609
pppol2tp_connect+0xbf5/0x1640 net/l2tp/l2tp_ppp.c:771
__sys_connect_file net/socket.c:2000 [inline]
__sys_connect+0x3da/0x460 net/socket.c:2017
__do_sys_connect net/socket.c:2027 [inline]
__se_sys_connect net/socket.c:2024 [inline]
__x64_sys_connect+0x7a/0x90 net/socket.c:2024
x64_sys_call+0x88d/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:43
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
Freed by task 1510:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
kasan_save_free_info+0x2b/0x40 mm/kasan/generic.c:516
____kasan_slab_free+0x132/0x180 mm/kasan/common.c:242
__kasan_slab_free+0x11/0x20 mm/kasan/common.c:250
kasan_slab_free include/linux/kasan.h:178 [inline]
slab_free_hook mm/slub.c:1750 [inline]
slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1776
slab_free mm/slub.c:3712 [inline]
__kmem_cache_free+0xb7/0x1b0 mm/slub.c:3728
kfree+0x6f/0xf0 mm/slab_common.c:990
l2tp_session_free net/l2tp/l2tp_core.c:168 [inline]
l2tp_session_put+0xaf/0x1a0 net/l2tp/l2tp_core.c:193
l2tp_session_delete+0x3df/0x4d0 net/l2tp/l2tp_core.c:1582
l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1228 [inline]
l2tp_tunnel_del_work+0x199/0x410 net/l2tp/l2tp_core.c:1266
process_one_work+0x717/0xc30 kernel/workqueue.c:2302
worker_thread+0xa4d/0x11d0 kernel/workqueue.c:2449
kthread+0x281/0x320 kernel/kthread.c:386
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
The buggy address belongs to the object at ffff88812c460800
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 0 bytes inside of
512-byte region [ffff88812c460800, ffff88812c460a00)
The buggy address belongs to the physical page:
page:ffffea0004b11800 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88812c463000 pfn:0x12c460
head:ffffea0004b11800 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 ffff888100040510 ffffea0004c83e08 ffff888100042f00
raw: ffff88812c463000 000000000010000b 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 2852, tgid 2850 (syz.2.646), ts 118182638219, free_ts 115540153740
set_page_owner include/linux/page_owner.h:33 [inline]
post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2672
prep_new_page+0x1c/0x110 mm/page_alloc.c:2679
get_page_from_freelist+0x2ca9/0x2d20 mm/page_alloc.c:4586
__alloc_pages+0x1fa/0x610 mm/page_alloc.c:5930
alloc_slab_page+0x6e/0xf0 include/linux/gfp.h:-1
allocate_slab mm/slub.c:1967 [inline]
new_slab+0x98/0x3e0 mm/slub.c:2020
___slab_alloc+0x70f/0xb70 mm/slub.c:3177
__slab_alloc+0x5e/0xa0 mm/slub.c:3263
slab_alloc_node mm/slub.c:3348 [inline]
__kmem_cache_alloc_node+0x204/0x2d0 mm/slub.c:3423
__do_kmalloc_node mm/slab_common.c:937 [inline]
__kmalloc+0xa4/0x1e0 mm/slab_common.c:951
kmalloc include/linux/slab.h:568 [inline]
io_alloc_async_data io_uring/io_uring.c:1598 [inline]
io_req_prep_async+0x28c/0x6c0 io_uring/io_uring.c:1619
io_queue_sqe_fallback+0x60/0x1b0 io_uring/io_uring.c:1949
io_submit_state_end io_uring/io_uring.c:2205 [inline]
io_submit_sqes+0x18eb/0x1ba0 io_uring/io_uring.c:2321
__do_sys_io_uring_enter io_uring/io_uring.c:3430 [inline]
__se_sys_io_uring_enter+0x32c/0x1f50 io_uring/io_uring.c:3362
__x64_sys_io_uring_enter+0xe5/0x100 io_uring/io_uring.c:3362
x64_sys_call+0x4b2/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:427
page last free stack trace:
reset_page_owner include/linux/page_owner.h:26 [inline]
free_pages_prepare mm/page_alloc.c:1580 [inline]
free_pcp_prepare mm/page_alloc.c:1654 [inline]
free_unref_page_prepare+0x80c/0x820 mm/page_alloc.c:3621
free_unref_page+0x93/0x530 mm/page_alloc.c:3719
free_the_page mm/page_alloc.c:863 [inline]
__free_pages+0x67/0x100 mm/page_alloc.c:6020
__vunmap+0xa3c/0xc00 mm/vmalloc.c:2739
__vfree mm/vmalloc.c:2788 [inline]
vfree+0x61/0x90 mm/vmalloc.c:2819
free_pg_vec net/packet/af_packet.c:4373 [inline]
packet_set_ring+0x197a/0x24a0 net/packet/af_packet.c:4594
packet_release+0x790/0xd20 net/packet/af_packet.c:3202
__sock_release net/socket.c:652 [inline]
sock_close+0xc9/0x220 net/socket.c:1389
__fput+0x1fd/0x8f0 fs/file_table.c:320
____fput+0x15/0x20 fs/file_table.c:348
task_work_run+0x1e1/0x250 kernel/task_work.c:203
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop+0x9b/0xb0 kernel/entry/common.c:177
exit_to_user_mode_prepare+0x87/0xd0 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:303
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x68/0xd2
Memory state around the buggy address:
ffff88812c460700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88812c460780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88812c460800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88812c460880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88812c460900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
------------[ cut here ]------------
WARNING: CPU: 1 PID: 5251 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: 5251 Comm: syz.0.1324 Tainted: G B syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:pppol2tp_sock_to_session+0x167/0x1b0 net/l2tp/l2tp_ppp.c:156
Code: 5d c3 e8 3c c2 d5 fc be 02 00 00 00 eb 0a e8 30 c2 d5 fc be 01 00 00 00 4c 89 f7 e8 03 21 cd fd e9 0f ff ff ff e8 19 c2 d5 fc <0f> 0b 48 89 df e8 ff 00 00 00 eb bd e8 08 c2 d5 fc 4c 89 f7 be 03
RSP: 0018:ffffc90003c7fb90 EFLAGS: 00010293
RAX: ffffffff849b9307 RBX: ffff88814cb24000 RCX: ffff8881158e6540
RDX: 0000000000000000 RSI: 0000000036ae3680 RDI: 000000000c04eb7d
RBP: ffffc90003c7fbb0 R08: ffffffff87b747e7 R09: 1ffffffff0f6e8fc
R10: dffffc0000000000 R11: fffffbfff0f6e8fd R12: dffffc0000000000
R13: dffffc0000000000 R14: 0000000036ae3680 R15: ffff88812c460800
FS: 0000000000000000(0000) GS:ffff8881f6f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd341fb7ff8 CR3: 000000012fad7000 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:434
__sock_release net/socket.c:652 [inline]
sock_close+0xc9/0x220 net/socket.c:1389
__fput+0x1fd/0x8f0 fs/file_table.c:320
____fput+0x15/0x20 fs/file_table.c:348
task_work_run+0x1e1/0x250 kernel/task_work.c:203
exit_task_work include/linux/task_work.h:39 [inline]
do_exit+0xa7c/0x27c0 kernel/exit.c:886
__do_sys_exit kernel/exit.c:995 [inline]
__se_sys_exit kernel/exit.c:993 [inline]
__x64_sys_exit+0x40/0x40 kernel/exit.c:993
x64_sys_call+0x67/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:61
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fd34119ce59
Code: Unable to access opcode bytes at 0x7fd34119ce2f.
RSP: 002b:00007fd341fd8fd8 EFLAGS: 00000246 ORIG_RAX: 000000000000003c
RAX: ffffffffffffffda RBX: 00007fd341415fa0 RCX: 00007fd34119ce59
RDX: 00007fd341fd99c8 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007fd341232d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd341416038 R14: 00007fd341415fa0 R15: 00007fff96bde3b8
---[ end trace 0000000000000000 ]---