==================================================================
BUG: KASAN: use-after-free in hlist_unhashed include/linux/list.h:854 [inline]
BUG: KASAN: use-after-free in hlist_del_init_rcu include/linux/rculist.h:183 [inline]
BUG: KASAN: use-after-free in l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1225 [inline]
BUG: KASAN: use-after-free in l2tp_tunnel_del_work+0xd8/0x410 net/l2tp/l2tp_core.c:1266
Read of size 8 at addr ffff888116ab6080 by task kworker/u4:14/3042
CPU: 0 PID: 3042 Comm: kworker/u4:14 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Workqueue: l2tp l2tp_tunnel_del_work
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_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:351
hlist_unhashed include/linux/list.h:854 [inline]
hlist_del_init_rcu include/linux/rculist.h:183 [inline]
l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1225 [inline]
l2tp_tunnel_del_work+0xd8/0x410 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
Allocated by task 3332:
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 3332:
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
pppol2tp_ioctl+0x748/0x960 net/l2tp/l2tp_ppp.c:-1
pppox_ioctl+0x1f6/0x330 drivers/net/ppp/pppox.c:93
sock_do_ioctl+0x114/0x330 net/socket.c:1191
sock_ioctl+0x475/0x700 net/socket.c:1310
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl+0x12f/0x1b0 fs/ioctl.c:856
__x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:856
x64_sys_call+0x58b/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:17
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
The buggy address belongs to the object at ffff888116ab6000
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 128 bytes inside of
512-byte region [ffff888116ab6000, ffff888116ab6200)
The buggy address belongs to the physical page:
page:ffffea00045aad00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x116ab4
head:ffffea00045aad00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 ffffea00045aac00 dead000000000003 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 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 2605, tgid 2602 (syz.3.649), ts 92886208692, free_ts 91829257911
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]
kzalloc include/linux/slab.h:699 [inline]
alloc_workqueue+0x15b/0x13b0 kernel/workqueue.c:4339
__ext4_fill_super fs/ext4/super.c:5440 [inline]
ext4_fill_super+0x5ac9/0x73e0 fs/ext4/super.c:5680
get_tree_bdev+0x450/0x6a0 fs/super.c:1371
ext4_get_tree+0x1c/0x20 fs/ext4/super.c:5710
vfs_get_tree+0x9a/0x270 fs/super.c:1578
do_new_mount+0x251/0xb40 fs/namespace.c:3081
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
__free_slab+0xc7/0x1a0 mm/slub.c:2044
free_slab mm/slub.c:2059 [inline]
discard_slab+0x29/0x40 mm/slub.c:2065
__slab_free+0x201/0x280 mm/slub.c:3625
do_slab_free mm/slub.c:3666 [inline]
___cache_free+0xbf/0xd0 mm/slub.c:3722
qlink_free mm/kasan/quarantine.c:168 [inline]
qlist_free_all+0xc6/0x140 mm/kasan/quarantine.c:187
kasan_quarantine_reduce+0x14a/0x170 mm/kasan/quarantine.c:294
__kasan_slab_alloc+0x24/0x80 mm/kasan/common.c:311
kasan_slab_alloc include/linux/kasan.h:202 [inline]
slab_post_alloc_hook+0x4f/0x2d0 mm/slab.h:768
slab_alloc_node mm/slub.c:3382 [inline]
slab_alloc mm/slub.c:3392 [inline]
__kmem_cache_alloc_lru mm/slub.c:3399 [inline]
kmem_cache_alloc+0x166/0x320 mm/slub.c:3408
vm_area_alloc+0x24/0x1a0 kernel/fork.c:497
__mmap_region mm/mmap.c:2862 [inline]
mmap_region+0xfab/0x2130 mm/mmap.c:3030
do_mmap+0x858/0xdd0 mm/mmap.c:1491
vm_mmap_pgoff+0x206/0x3f0 mm/util.c:525
Memory state around the buggy address:
ffff888116ab5f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888116ab6000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888116ab6080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888116ab6100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888116ab6180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 0 PID: 3042 at lib/refcount.c:28 refcount_warn_saturate+0x120/0x1a0 lib/refcount.c:28
Modules linked in:
CPU: 0 PID: 3042 Comm: kworker/u4:14 Tainted: G B W syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Workqueue: l2tp l2tp_tunnel_del_work
RIP: 0010:refcount_warn_saturate+0x120/0x1a0 lib/refcount.c:28
Code: 05 01 48 c7 c7 80 0b ca 85 e8 fc 2c d9 fe 0f 0b eb c3 e8 43 9c 08 ff c6 05 34 cc 26 05 01 48 c7 c7 e0 0b ca 85 e8 e0 2c d9 fe <0f> 0b eb a7 e8 27 9c 08 ff c6 05 15 cc 26 05 01 48 c7 c7 20 0b ca
RSP: 0018:ffffc90000b17c38 EFLAGS: 00010246
RAX: 141c6247a6baa300 RBX: 0000000000000003 RCX: ffff88810b8f2880
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000002
RBP: ffffc90000b17c48 R08: ffffc90000b17827 R09: 1ffff92000162f04
R10: dffffc0000000000 R11: fffff52000162f05 R12: ffff88810fb58020
R13: dffffc0000000000 R14: 0000000000000003 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff8881f6e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000002200 CR3: 000000000700f000 CR4: 00000000003506b0
Call Trace:
__refcount_sub_and_test include/linux/refcount.h:283 [inline]
__refcount_dec_and_test include/linux/refcount.h:315 [inline]
refcount_dec_and_test include/linux/refcount.h:333 [inline]
l2tp_session_put+0xc8/0x1a0 net/l2tp/l2tp_core.c:192
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
---[ end trace 0000000000000000 ]---
device bridge_slave_1 left promiscuous mode
bridge0: port 2(bridge_slave_1) entered disabled state
device bridge_slave_0 left promiscuous mode
bridge0: port 1(bridge_slave_0) entered disabled state
device veth1_macvtap left promiscuous mode
device veth0_vlan left promiscuous mode
tipc: Left network mode
device bridge_slave_1 left promiscuous mode
bridge0: port 2(bridge_slave_1) entered disabled state
device bridge_slave_0 left promiscuous mode
bridge0: port 1(bridge_slave_0) entered disabled state
device bridge_slave_1 left promiscuous mode
bridge0: port 2(bridge_slave_1) entered disabled state
device bridge_slave_0 left promiscuous mode
bridge0: port 1(bridge_slave_0) entered disabled state
device veth1_macvtap left promiscuous mode
device veth0_vlan left promiscuous mode
device veth1_macvtap left promiscuous mode
device veth0_vlan left promiscuous mode