==================================================================
BUG: KASAN: use-after-free in pppol2tp_sock_to_session+0x1a0/0x1b0 net/l2tp/l2tp_ppp.c:156
Read of size 4 at addr ffff888108bfb400 by task syz.5.1981/8010
CPU: 0 PID: 8010 Comm: syz.5.1981 Tainted: G W 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_sendmsg+0xdf/0x5d0 net/l2tp/l2tp_ppp.c:270
sock_sendmsg_nosec net/socket.c:716 [inline]
__sock_sendmsg net/socket.c:728 [inline]
sock_write_iter+0x2ea/0x3f0 net/socket.c:1133
do_iter_readv_writev fs/read_write.c:-1 [inline]
do_iter_write+0x65a/0xb30 fs/read_write.c:861
vfs_writev+0x339/0x5f0 fs/read_write.c:934
do_writev+0x14e/0x2c0 fs/read_write.c:977
__do_sys_writev fs/read_write.c:1050 [inline]
__se_sys_writev fs/read_write.c:1047 [inline]
__x64_sys_writev+0x7d/0x90 fs/read_write.c:1047
x64_sys_call+0xad/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:21
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: 0033:0x7f451219ce59
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:00007f4513073028 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 00007f4512415fa0 RCX: 00007f451219ce59
RDX: 0000000000000001 RSI: 0000200000000180 RDI: 0000000000000003
RBP: 00007f4512232d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4512416038 R14: 00007f4512415fa0 R15: 00007ffe00158848
Allocated by task 8010:
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 8010:
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
Last potentially related work creation:
kasan_save_stack+0x3a/0x60 mm/kasan/common.c:46
__kasan_record_aux_stack+0xb6/0xc0 mm/kasan/generic.c:486
kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:496
kvfree_call_rcu+0x8b/0x7a0 kernel/rcu/tree.c:3445
inet6_ifa_finish_destroy+0x129/0x1b0 net/ipv6/addrconf.c:1007
in6_ifa_put include/net/addrconf.h:459 [inline]
addrconf_ifdown+0x1254/0x1950 net/ipv6/addrconf.c:3960
addrconf_notify+0x39f/0xe30 net/ipv6/addrconf.c:-1
notifier_call_chain kernel/notifier.c:87 [inline]
raw_notifier_call_chain+0xa1/0x110 kernel/notifier.c:455
call_netdevice_notifiers_info net/core/dev.c:2022 [inline]
call_netdevice_notifiers_extack net/core/dev.c:2060 [inline]
call_netdevice_notifiers net/core/dev.c:2074 [inline]
dev_close_many+0x325/0x4d0 net/core/dev.c:1622
unregister_netdevice_many+0x43f/0x1910 net/core/dev.c:10979
unregister_netdevice_queue+0x2e1/0x320 net/core/dev.c:10936
unregister_netdevice include/linux/netdevice.h:3109 [inline]
__tun_detach+0xc9d/0x1450 drivers/net/tun.c:685
tun_detach drivers/net/tun.c:701 [inline]
tun_chr_close+0x92/0x140 drivers/net/tun.c:3492
__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
Second to last potentially related work creation:
kasan_save_stack+0x3a/0x60 mm/kasan/common.c:46
__kasan_record_aux_stack+0xb6/0xc0 mm/kasan/generic.c:486
kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:496
insert_work+0x51/0x300 kernel/workqueue.c:1368
__queue_work+0x9d0/0xd50 kernel/workqueue.c:1527
__queue_delayed_work+0x188/0x200 kernel/workqueue.c:1675
mod_delayed_work_on+0x74/0xe0 kernel/workqueue.c:1749
mod_delayed_work include/linux/workqueue.h:540 [inline]
addrconf_mod_dad_work+0x7d/0x120 net/ipv6/addrconf.c:335
addrconf_dad_start net/ipv6/addrconf.c:4139 [inline]
addrconf_add_linklocal+0x482/0x660 net/ipv6/addrconf.c:3287
addrconf_addr_gen+0x51f/0x690 net/ipv6/addrconf.c:3402
addrconf_dev_config net/ipv6/addrconf.c:3459 [inline]
addrconf_init_auto_addrs+0x872/0xbc0 net/ipv6/addrconf.c:3538
addrconf_notify+0x7fe/0xe30 net/ipv6/addrconf.c:3711
notifier_call_chain kernel/notifier.c:87 [inline]
raw_notifier_call_chain+0xa1/0x110 kernel/notifier.c:455
call_netdevice_notifiers_info net/core/dev.c:2022 [inline]
call_netdevice_notifiers_extack net/core/dev.c:2060 [inline]
call_netdevice_notifiers net/core/dev.c:2074 [inline]
__dev_notify_flags+0x2f4/0x5b0 net/core/dev.c:8730
dev_change_flags+0xe3/0x1a0 net/core/dev.c:8768
dev_ifsioc+0x130/0xd90 net/core/dev_ioctl.c:326
dev_ioctl+0x53c/0xcf0 net/core/dev_ioctl.c:572
sock_do_ioctl+0x252/0x330 net/socket.c:1205
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 ffff888108bfb400
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 0 bytes inside of
512-byte region [ffff888108bfb400, ffff888108bfb600)
The buggy address belongs to the physical page:
page:ffffea000422fe00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x108bf8
head:ffffea000422fe00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 ffffea00043cdb00 dead000000000002 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 1332391360, free_ts 1332391360
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_node_track_caller+0xa1/0x1e0 mm/slab_common.c:958
__do_krealloc mm/slab_common.c:1341 [inline]
krealloc+0x6f/0x110 mm/slab_common.c:1374
add_sysfs_param+0xce/0x830 kernel/params.c:651
kernel_add_sysfs_param+0xb1/0x12e kernel/params.c:812
param_sysfs_builtin+0x20d/0x2ae kernel/params.c:851
param_sysfs_init+0x6a/0x6f kernel/params.c:972
do_one_initcall+0x1d6/0x580 init/main.c:1433
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_pages+0x82/0x90 mm/page_alloc.c:6031
__stack_depot_save+0x45f/0x490 lib/stackdepot.c:506
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_set_track+0x60/0x70 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]
kmalloc_trace+0x40/0xb0 mm/slab_common.c:1033
kmalloc include/linux/slab.h:563 [inline]
kzalloc include/linux/slab.h:699 [inline]
dev_pm_qos_constraints_allocate+0x93/0x3f0 drivers/base/power/qos.c:206
__dev_pm_qos_add_request+0x132/0x3e0 drivers/base/power/qos.c:346
dev_pm_qos_add_request drivers/base/power/qos.c:396 [inline]
dev_pm_qos_expose_latency_limit+0xd3/0x2b0 drivers/base/power/qos.c:715
register_cpu+0x2da/0x3c0 drivers/base/cpu.c:385
arch_register_cpu+0x13d/0x310 arch/x86/kernel/topology.c:136
topology_init+0x57/0xa4 arch/x86/kernel/topology.c:158
do_one_initcall+0x1d6/0x580 init/main.c:1433
Memory state around the buggy address:
ffff888108bfb300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888108bfb380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888108bfb400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888108bfb480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888108bfb500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
------------[ cut here ]------------
WARNING: CPU: 0 PID: 8010 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: 8010 Comm: syz.5.1981 Tainted: G B W 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:ffffc9000183f8f8 EFLAGS: 00010246
RAX: ffffffff849b9307 RBX: ffff88811cb6b000 RCX: 0000000000080000
RDX: ffffc9000326e000 RSI: 000000000007ffff RDI: 0000000000080000
RBP: ffffc9000183f918 R08: ffffffff87b747e7 R09: 1ffffffff0f6e8fc
R10: dffffc0000000000 R11: fffffbfff0f6e8fd R12: dffffc0000000000
R13: 00000000001fffa2 R14: 000000004f460000 R15: ffff888108bfb400
FS: 00007f45130736c0(0000) GS:ffff8881f6e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f4513052000 CR3: 00000001148a3000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
pppol2tp_sendmsg+0xdf/0x5d0 net/l2tp/l2tp_ppp.c:270
sock_sendmsg_nosec net/socket.c:716 [inline]
__sock_sendmsg net/socket.c:728 [inline]
sock_write_iter+0x2ea/0x3f0 net/socket.c:1133
do_iter_readv_writev fs/read_write.c:-1 [inline]
do_iter_write+0x65a/0xb30 fs/read_write.c:861
vfs_writev+0x339/0x5f0 fs/read_write.c:934
do_writev+0x14e/0x2c0 fs/read_write.c:977
__do_sys_writev fs/read_write.c:1050 [inline]
__se_sys_writev fs/read_write.c:1047 [inline]
__x64_sys_writev+0x7d/0x90 fs/read_write.c:1047
x64_sys_call+0xad/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:21
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: 0033:0x7f451219ce59
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:00007f4513073028 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 00007f4512415fa0 RCX: 00007f451219ce59
RDX: 0000000000000001 RSI: 0000200000000180 RDI: 0000000000000003
RBP: 00007f4512232d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4512416038 R14: 00007f4512415fa0 R15: 00007ffe00158848
---[ end trace 0000000000000000 ]---