==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff888135157590 by task udevd/326
CPU: 1 PID: 326 Comm: udevd Tainted: G W syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
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_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:351
rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
rcu_do_batch+0x4bc/0xc30 kernel/rcu/tree.c:2285
rcu_core+0x486/0xf00 kernel/rcu/tree.c:2557
rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2574
handle_softirqs+0x1d7/0x600 kernel/softirq.c:642
__do_softirq kernel/softirq.c:680 [inline]
invoke_softirq kernel/softirq.c:497 [inline]
__irq_exit_rcu+0x52/0xf0 kernel/softirq.c:729
irq_exit_rcu+0x9/0x10 kernel/softirq.c:741
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
sysvec_apic_timer_interrupt+0xa9/0xc0 arch/x86/kernel/apic/apic.c:1118
asm_sysvec_apic_timer_interrupt+0x1b/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0x55/0x80 kernel/locking/spinlock.c:194
Code: 80 db 0d 87 e8 7c f1 b5 fc 4c 89 f7 48 83 3d 01 dc 0c 02 00 74 30 e8 9e 0d 00 00 90 f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 d6 96 4b fc 65 8b 05 27 6e 01 7b 85 c0 74 05 5b 41 5e 5d c3 e8
RSP: 0018:ffffc9000dcdfc60 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000a06 RCX: dffffc0000000000
RDX: ffff88810e259440 RSI: 0000000000000a06 RDI: 0000000000000001
RBP: ffffc9000dcdfc70 R08: ffffffff8792e0af R09: 1ffffffff0f25c15
R10: dffffc0000000000 R11: fffffbfff0f25c16 R12: ffff88811038c420
R13: 0000000000000a06 R14: 0000000000000003 R15: 0000000000000000
spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
__wake_up_common_lock kernel/sched/wait.c:141 [inline]
__wake_up+0x12e/0x1a0 kernel/sched/wait.c:161
fsnotify_insert_event+0x314/0x3d0 fs/notify/notification.c:127
fsnotify_add_event include/linux/fsnotify_backend.h:629 [inline]
inotify_handle_inode_event+0x353/0x4e0 fs/notify/inotify/inotify_fsnotify.c:126
inotify_ignored_and_remove_idr+0x29/0x70 fs/notify/inotify/inotify_user.c:527
inotify_freeing_mark+0x1d/0x30 fs/notify/inotify/inotify_fsnotify.c:140
fsnotify_free_mark fs/notify/mark.c:516 [inline]
fsnotify_destroy_mark+0x260/0x370 fs/notify/mark.c:525
__do_sys_inotify_rm_watch fs/notify/inotify/inotify_user.c:835 [inline]
__se_sys_inotify_rm_watch+0x164/0x230 fs/notify/inotify/inotify_user.c:812
__x64_sys_inotify_rm_watch+0x5b/0x70 fs/notify/inotify/inotify_user.c:812
x64_sys_call+0x6d4/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:256
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: 0033:0x7f1189721a07
Code: 73 01 c3 48 8b 0d f1 f3 0c 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 ff 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d c1 f3 0c 00 f7 d8 64 89 01 48
RSP: 002b:00007ffe75256a48 EFLAGS: 00000246 ORIG_RAX: 00000000000000ff
RAX: ffffffffffffffda RBX: 0000563bcaaddbb0 RCX: 00007f1189721a07
RDX: 0000000000000007 RSI: 0000000000000221 RDI: 0000000000000007
RBP: 0000000000000221 R08: 00000000000001e0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffe75256a50
R13: 0000000003938700 R14: 0000563b97143100 R15: 0000563b97143140
Allocated by task 1212:
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 43:
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
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
__call_rcu_common kernel/rcu/tree.c:2807 [inline]
call_rcu+0xcf/0xf50 kernel/rcu/tree.c:2926
pppol2tp_release+0x1e3/0x2b0 net/l2tp/l2tp_ppp.c:446
__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+0xaf2/0x2850 kernel/exit.c:887
do_group_exit+0x21b/0x2e0 kernel/exit.c:1030
get_signal+0x167c/0x1700 kernel/signal.c:2895
arch_do_signal_or_restart+0xd1/0x11c0 arch/x86/kernel/signal.c:871
exit_to_user_mode_loop+0x7a/0xb0 kernel/entry/common.c:174
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
The buggy address belongs to the object at ffff888135157400
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
512-byte region [ffff888135157400, ffff888135157600)
The buggy address belongs to the physical page:
page:ffffea0004d45500 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x135154
head:ffffea0004d45500 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 0000000000000000 dead000000000001 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 0x1d2a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 60, tgid 60 (kworker/1:2), ts 35052052685, free_ts 32217155656
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
kmalloc_reserve net/core/skbuff.c:449 [inline]
__alloc_skb+0x226/0x4a0 net/core/skbuff.c:518
alloc_skb include/linux/skbuff.h:1322 [inline]
ndisc_alloc_skb net/ipv6/ndisc.c:423 [inline]
ndisc_ns_create+0x26e/0x920 net/ipv6/ndisc.c:626
ndisc_send_ns+0xb7/0x160 net/ipv6/ndisc.c:668
addrconf_dad_work+0x9d6/0x14a0 net/ipv6/addrconf.c:4245
process_one_work+0x717/0xc30 kernel/workqueue.c:2302
worker_thread+0xa4d/0x11d0 kernel/workqueue.c:2449
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_pages_ok+0xb87/0xc80 mm/page_alloc.c:1838
free_the_page mm/page_alloc.c:865 [inline]
free_compound_page+0xaa/0xd0 mm/page_alloc.c:886
destroy_large_folio+0x68/0xa0 mm/page_alloc.c:923
__folio_put_large mm/swap.c:113 [inline]
__folio_put+0xd1/0xe0 mm/swap.c:121
folio_put include/linux/mm.h:1442 [inline]
put_page include/linux/mm.h:1494 [inline]
io_pages_unmap+0x249/0x3a0 io_uring/io_uring.c:2521
io_rings_free+0x51/0xe0 io_uring/io_uring.c:2532
io_ring_ctx_free+0x76b/0x987 io_uring/io_uring.c:2762
io_ring_exit_work+0x6cd/0x724 io_uring/io_uring.c:2936
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
Memory state around the buggy address:
ffff888135157480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888135157500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888135157580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888135157600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888135157680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
0: 80 db 0d sbb $0xd,%bl
3: 87 e8 xchg %ebp,%eax
5: 7c f1 jl 0xfffffff8
7: b5 fc mov $0xfc,%ch
9: 4c 89 f7 mov %r14,%rdi
c: 48 83 3d 01 dc 0c 02 cmpq $0x0,0x20cdc01(%rip) # 0x20cdc15
13: 00
14: 74 30 je 0x46
16: e8 9e 0d 00 00 call 0xdb9
1b: 90 nop
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 d6 96 4b fc call 0xfc4b9705 <-- trapping instruction
2f: 65 8b 05 27 6e 01 7b mov %gs:0x7b016e27(%rip),%eax # 0x7b016e5d
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