==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff88810d77e190 by task kworker/u4:59/7827
CPU: 0 PID: 7827 Comm: kworker/u4:59 Tainted: G W syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Workqueue: events_unbound fsnotify_mark_destroy_workfn
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_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:309
rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
rcu_do_batch+0x47d/0xbf0 kernel/rcu/tree.c:2512
rcu_core+0x4a3/0xef0 kernel/rcu/tree.c:2763
rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2776
handle_softirqs+0x250/0x560 kernel/softirq.c:583
__do_softirq kernel/softirq.c:621 [inline]
invoke_softirq kernel/softirq.c:443 [inline]
__irq_exit_rcu+0x52/0xf0 kernel/softirq.c:670
irq_exit_rcu+0x9/0x10 kernel/softirq.c:682
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
sysvec_apic_timer_interrupt+0xa9/0xc0 arch/x86/kernel/apic/apic.c:1108
asm_sysvec_apic_timer_interrupt+0x1b/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0x56/0x80 kernel/locking/spinlock.c:194
Code: 46 6d 86 e8 0c a6 f5 fc 4c 89 f7 48 83 3d a9 d0 b9 01 00 74 31 e8 3e 72 9c fc 66 90 f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 f5 43 94 fc 65 8b 05 16 f7 4e 7b 85 c0 74 05 5b 41 5e 5d c3 e8
RSP: 0000:ffffc900010efa50 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000a02 RCX: dffffc0000000000
RDX: 0000000000000000 RSI: 0000000000000a02 RDI: 0000000000000001
RBP: ffffc900010efa60 R08: ffffffff86e945ef R09: 1ffffffff0dd28bd
R10: dffffc0000000000 R11: fffffbfff0dd28be R12: ffffffff87122470
R13: dffffc0000000000 R14: ffffffff871224e8 R15: ffff888100057400
spin_unlock_irqrestore include/linux/spinlock.h:419 [inline]
srcu_funnel_gp_start kernel/rcu/srcutree.c:687 [inline]
srcu_gp_start_if_needed+0x5ea/0x940 kernel/rcu/srcutree.c:838
__call_srcu kernel/rcu/srcutree.c:883 [inline]
__synchronize_srcu+0x176/0x210 kernel/rcu/srcutree.c:929
synchronize_srcu+0x1cb/0x1e0 kernel/rcu/srcutree.c:-1
fsnotify_mark_destroy_workfn+0x106/0x2e0 fs/notify/mark.c:887
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
Allocated by task 9471:
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 7827:
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
__call_rcu_common kernel/rcu/tree.c:3011 [inline]
call_rcu+0x10b/0xf60 kernel/rcu/tree.c:3129
pppol2tp_release+0x1e3/0x2b0 net/l2tp/l2tp_ppp.c:447
__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
tracehook_notify_resume include/linux/tracehook.h:189 [inline]
exit_to_user_mode_loop+0xd0/0xe0 kernel/entry/common.c:181
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
Second to 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
kvfree_call_rcu+0xb6/0x860 kernel/rcu/tree.c:3648
drop_sysctl_table+0x2f5/0x430 fs/proc/proc_sysctl.c:1687
drop_sysctl_table+0x2e4/0x430 fs/proc/proc_sysctl.c:1690
unregister_sysctl_table+0x7a/0x120 fs/proc/proc_sysctl.c:1725
unregister_net_sysctl_table+0x15/0x20 net/sysctl_net.c:175
__addrconf_sysctl_unregister net/ipv6/addrconf.c:7193 [inline]
addrconf_sysctl_unregister net/ipv6/addrconf.c:7221 [inline]
addrconf_ifdown+0x15bf/0x1910 net/ipv6/addrconf.c:3952
addrconf_notify+0x3bd/0xe00 net/ipv6/addrconf.c:-1
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 net/core/dev.c:2096 [inline]
unregister_netdevice_many+0x103d/0x1a00 net/core/dev.c:11176
vti6_exit_batch_net+0x273/0x2c0 net/ipv6/ip6_vti.c:1190
ops_exit_list net/core/net_namespace.c:177 [inline]
cleanup_net+0x605/0xae0 net/core/net_namespace.c:599
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 ffff88810d77e000
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
512-byte region [ffff88810d77e000, ffff88810d77e200)
The buggy address belongs to the page:
page:ffffea000435df00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10d77c
head:ffffea000435df00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 0000000000000000 0000000100000001 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 6312, ts 293792223367, free_ts 292410269960
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]
__kmalloc_track_caller+0x169/0x2c0 mm/slub.c:4954
kmalloc_reserve net/core/skbuff.c:357 [inline]
__alloc_skb+0x210/0x730 net/core/skbuff.c:428
alloc_skb include/linux/skbuff.h:1183 [inline]
nlmsg_new include/net/netlink.h:953 [inline]
netlink_ack+0x35c/0xb10 net/netlink/af_netlink.c:2446
netlink_rcv_skb+0x267/0x430 net/netlink/af_netlink.c:2517
rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:5671
netlink_unicast_kernel net/netlink/af_netlink.c:1322 [inline]
netlink_unicast+0x86c/0xa30 net/netlink/af_netlink.c:1348
netlink_sendmsg+0x879/0xb80 net/netlink/af_netlink.c:1922
sock_sendmsg_nosec net/socket.c:704 [inline]
__sock_sendmsg net/socket.c:716 [inline]
__sys_sendto+0x46d/0x620 net/socket.c:2062
__do_sys_sendto net/socket.c:2074 [inline]
__se_sys_sendto net/socket.c:2070 [inline]
__x64_sys_sendto+0xe5/0x100 net/socket.c:2070
page last free stack trace:
reset_page_owner include/linux/page_owner.h:26 [inline]
free_pages_prepare mm/page_alloc.c:1474 [inline]
free_pcp_prepare mm/page_alloc.c:1546 [inline]
free_unref_page_prepare+0x5fa/0x600 mm/page_alloc.c:3536
free_unref_page+0xae/0x540 mm/page_alloc.c:3618
free_the_page mm/page_alloc.c:805 [inline]
__free_pages+0x6c/0x100 mm/page_alloc.c:5900
__free_slab+0xe5/0x1e0 mm/slub.c:2025
free_slab mm/slub.c:2040 [inline]
discard_slab mm/slub.c:2046 [inline]
__unfreeze_partials+0x15a/0x190 mm/slub.c:2532
put_cpu_partial+0xc6/0x120 mm/slub.c:2612
__slab_free+0x1d4/0x290 mm/slub.c:3395
do_slab_free mm/slub.c:3514 [inline]
___cache_free+0x104/0x120 mm/slub.c:3535
qlink_free+0x4d/0x90 mm/kasan/quarantine.c:157
qlist_free_all+0x5f/0xb0 mm/kasan/quarantine.c:176
kasan_quarantine_reduce+0x14a/0x170 mm/kasan/quarantine.c:283
__kasan_slab_alloc+0x2f/0xe0 mm/kasan/common.c:443
kasan_slab_alloc include/linux/kasan.h:217 [inline]
slab_post_alloc_hook+0x4f/0x2b0 mm/slab.h:550
slab_alloc_node mm/slub.c:3245 [inline]
slab_alloc mm/slub.c:3255 [inline]
kmem_cache_alloc+0xf7/0x260 mm/slub.c:3260
kmem_cache_alloc_node include/linux/slab.h:492 [inline]
__alloc_skb+0xe4/0x730 net/core/skbuff.c:416
alloc_skb include/linux/skbuff.h:1183 [inline]
netlink_alloc_large_skb net/netlink/af_netlink.c:1186 [inline]
netlink_sendmsg+0x611/0xb80 net/netlink/af_netlink.c:1897
Memory state around the buggy address:
ffff88810d77e080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88810d77e100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88810d77e180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88810d77e200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88810d77e280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
0: 46 6d rex.RX insl (%dx),%es:(%rdi)
2: 86 e8 xchg %ch,%al
4: 0c a6 or $0xa6,%al
6: f5 cmc
7: fc cld
8: 4c 89 f7 mov %r14,%rdi
b: 48 83 3d a9 d0 b9 01 cmpq $0x0,0x1b9d0a9(%rip) # 0x1b9d0bc
12: 00
13: 74 31 je 0x46
15: e8 3e 72 9c fc call 0xfc9c7258
1a: 66 90 xchg %ax,%ax
1c: f7 c3 00 02 00 00 test $0x200,%ebx
22: 74 01 je 0x25
24: fb sti
25: bf 01 00 00 00 mov $0x1,%edi
* 2a: e8 f5 43 94 fc call 0xfc944424 <-- trapping instruction
2f: 65 8b 05 16 f7 4e 7b mov %gs:0x7b4ef716(%rip),%eax # 0x7b4ef74c
36: 85 c0 test %eax,%eax
38: 74 05 je 0x3f
3a: 5b pop %rbx
3b: 41 5e pop %r14
3d: 5d pop %rbp
3e: c3 ret
3f: e8 .byte 0xe8