==================================================================
BUG: KASAN: use-after-free in pppol2tp_sock_to_session+0x1a0/0x1b0 net/l2tp/l2tp_ppp.c:156
Read of size 4 at addr ffff888128f24c00 by task syz.8.254/1215
CPU: 0 PID: 1215 Comm: syz.8.254 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
__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:1335
__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
exit_task_work include/linux/task_work.h:33 [inline]
do_exit+0xb70/0x29a0 kernel/exit.c:890
do_group_exit+0x149/0x310 kernel/exit.c:1004
get_signal+0x64f/0x1430 kernel/signal.c:2907
arch_do_signal_or_restart+0xe2/0x1100 arch/x86/kernel/signal.c:867
handle_signal_work kernel/entry/common.c:154 [inline]
exit_to_user_mode_loop+0xa7/0xe0 kernel/entry/common.c:178
exit_to_user_mode_prepare+0x87/0xd0 kernel/entry/common.c:214
__syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:307
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fdb721eee59
Code: Unable to access opcode bytes at RIP 0x7fdb721eee2f.
RSP: 002b:00007fdb70c490e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: 0000000000000001 RBX: 00007fdb72467fa8 RCX: 00007fdb721eee59
RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 00007fdb72467fac
RBP: 00007fdb72467fa0 R08: 00322387769fafa9 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdb72468038 R14: 00007ffdb2fe1530 R15: 00007ffdb2fe1618
Allocated by task 1215:
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:1922 [inline]
__sys_connect+0x3cb/0x450 net/socket.c:1939
__do_sys_connect net/socket.c:1949 [inline]
__se_sys_connect net/socket.c:1946 [inline]
__x64_sys_connect+0x7a/0x90 net/socket.c:1946
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 306:
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
The buggy address belongs to the object at ffff888128f24c00
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 0 bytes inside of
512-byte region [ffff888128f24c00, ffff888128f24e00)
The buggy address belongs to the page:
page:ffffea0004a3c900 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x128f24
head:ffffea0004a3c900 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 dead000000000100 dead000000000122 ffff888100042f00
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 288, ts 24085805173, free_ts 0
set_page_owner include/linux/page_owner.h:33 [inline]
post_alloc_hook+0x192/0x1b0 mm/page_alloc.c:2607
prep_new_page+0x1c/0x110 mm/page_alloc.c:2613
get_page_from_freelist+0x2c3a/0x2cd0 mm/page_alloc.c:4487
__alloc_pages+0x1a2/0x460 mm/page_alloc.c:5824
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]
kmem_cache_alloc_trace+0x146/0x270 mm/slub.c:3272
kmalloc include/linux/slab.h:619 [inline]
kzalloc include/linux/slab.h:750 [inline]
inetdev_init+0x81/0x500 net/ipv4/devinet.c:266
inetdev_event+0x1f4/0x1060 net/ipv4/devinet.c:1544
notifier_call_chain kernel/notifier.c:83 [inline]
raw_notifier_call_chain+0x90/0x100 kernel/notifier.c:391
call_netdevice_notifiers_info net/core/dev.c:2070 [inline]
call_netdevice_notifiers_extack net/core/dev.c:2082 [inline]
call_netdevice_notifiers+0x119/0x190 net/core/dev.c:2096
register_netdevice+0x110a/0x1490 net/core/dev.c:10462
veth_newlink+0x6af/0xe20 drivers/net/veth.c:1683
__rtnl_newlink net/core/rtnetlink.c:3527 [inline]
rtnl_newlink+0x137f/0x1900 net/core/rtnetlink.c:3575
rtnetlink_rcv_msg+0x9fd/0xcb0 net/core/rtnetlink.c:5653
page_owner free stack trace missing
Memory state around the buggy address:
ffff888128f24b00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888128f24b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888128f24c00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888128f24c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888128f24d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
------------[ cut here ]------------
WARNING: CPU: 1 PID: 1215 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: 1215 Comm: syz.8.254 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 cc f2 0b fd be 02 00 00 00 eb 0a e8 c0 f2 0b fd be 01 00 00 00 4c 89 f7 e8 13 62 f2 fd e9 0f ff ff ff e8 a9 f2 0b fd <0f> 0b 48 89 df e8 ef 00 00 00 eb bd e8 98 f2 0b fd 4c 89 f7 be 03
RSP: 0018:ffffc90000c5f890 EFLAGS: 00010293
RAX: ffffffff845db907 RBX: ffff88810b278000 RCX: ffff8881184a13c0
RDX: 0000000000000000 RSI: 00000000120e9000 RDI: 000000000c04eb7d
RBP: ffffc90000c5f8b0 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff0e18c4c R12: dffffc0000000000
R13: dffffc0000000000 R14: 00000000120e9000 R15: ffff888128f24c00
FS: 0000000000000000(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff1e934f000 CR3: 000000012a2ef000 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:649 [inline]
sock_close+0xb8/0x200 net/socket.c:1335
__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
exit_task_work include/linux/task_work.h:33 [inline]
do_exit+0xb70/0x29a0 kernel/exit.c:890
do_group_exit+0x149/0x310 kernel/exit.c:1004
get_signal+0x64f/0x1430 kernel/signal.c:2907
arch_do_signal_or_restart+0xe2/0x1100 arch/x86/kernel/signal.c:867
handle_signal_work kernel/entry/common.c:154 [inline]
exit_to_user_mode_loop+0xa7/0xe0 kernel/entry/common.c:178
exit_to_user_mode_prepare+0x87/0xd0 kernel/entry/common.c:214
__syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:307
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fdb721eee59
Code: Unable to access opcode bytes at RIP 0x7fdb721eee2f.
RSP: 002b:00007fdb70c490e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: 0000000000000001 RBX: 00007fdb72467fa8 RCX: 00007fdb721eee59
RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 00007fdb72467fac
RBP: 00007fdb72467fa0 R08: 00322387769fafa9 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdb72468038 R14: 00007ffdb2fe1530 R15: 00007ffdb2fe1618
---[ end trace c7201e6148a1f8b2 ]---