==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff88813469c990 by task syz.3.15/354
CPU: 1 PID: 354 Comm: syz.3.15 Not tainted 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:finish_task_switch+0x173/0x7c0 kernel/sched/core.c:5302
Code: 80 3c 2b 00 74 08 4c 89 f7 e8 99 8a 69 00 4d 8b 2e 4d 85 ed 0f 85 cd 00 00 00 4c 89 e7 e8 55 98 b3 03 fb 49 8d 9f 48 0b 00 00 <48> 89 d8 48 c1 e8 03 49 bd 00 00 00 00 00 fc ff df 42 0f b6 04 28
RSP: 0018:ffffc9000ddcf528 EFLAGS: 00000282
RAX: 0000000080000001 RBX: ffff888114480b48 RCX: 0000000000000000
RDX: 0000000000000001 RSI: ffffffff85ca6940 RDI: 00000000ffffffff
RBP: ffffc9000ddcf570 R08: ffff88811512a887 R09: 1ffff11022a25510
R10: dffffc0000000000 R11: ffffed1022a25511 R12: ffff8881f6f37d80
R13: 0000000000000000 R14: ffff8881f6f388e0 R15: ffff888114480000
context_switch kernel/sched/core.c:5428 [inline]
__schedule+0xbea/0x14b0 kernel/sched/core.c:6755
preempt_schedule_common+0x9b/0xf0 kernel/sched/core.c:6924
preempt_schedule+0xbc/0xd0 kernel/sched/core.c:6948
preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:34
__raw_spin_unlock include/linux/spinlock_api_smp.h:143 [inline]
_raw_spin_unlock+0x5f/0x70 kernel/locking/spinlock.c:186
spin_unlock include/linux/spinlock.h:391 [inline]
zap_pte_range mm/memory.c:1540 [inline]
zap_pmd_range mm/memory.c:1599 [inline]
zap_pud_range mm/memory.c:1628 [inline]
zap_p4d_range mm/memory.c:1649 [inline]
unmap_page_range+0x20e5/0x2360 mm/memory.c:1670
unmap_single_vma mm/memory.c:1716 [inline]
unmap_vmas+0x34c/0x480 mm/memory.c:1756
exit_mmap+0x2a4/0xc10 mm/mmap.c:3371
__mmput+0x92/0x340 kernel/fork.c:1319
mmput+0x4b/0x150 kernel/fork.c:1343
exit_mm kernel/exit.c:569 [inline]
do_exit+0xa51/0x2850 kernel/exit.c:874
do_group_exit+0x21b/0x2e0 kernel/exit.c:1030
__do_sys_exit_group kernel/exit.c:1041 [inline]
__se_sys_exit_group kernel/exit.c:1039 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1039
x64_sys_call+0x7b4/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:232
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: 0033:0x7f91b079e0d9
Code: Unable to access opcode bytes at 0x7f91b079e0af.
RSP: 002b:00007fff159064f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f91b079e0d9
RDX: 0000000000000064 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007fff1590655c R08: 0000000000000006 R09: 00000000000927c0
R10: 00000000005fa8b4 R11: 0000000000000246 R12: 0000000000000002
R13: 00000000000927c0 R14: 00000000000066ed R15: 00007fff159065b0
Allocated by task 388:
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 308:
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
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
The buggy address belongs to the object at ffff88813469c800
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
512-byte region [ffff88813469c800, ffff88813469ca00)
The buggy address belongs to the physical page:
page:ffffea0004d1a700 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x13469c
head:ffffea0004d1a700 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 0000000000000000 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 0x1d2a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 315, tgid 315 (kworker/1:4), ts 26992157969, free_ts 0
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_send_rs+0x31d/0x870 net/ipv6/ndisc.c:707
addrconf_dad_completed+0x958/0xe80 net/ipv6/addrconf.c:4322
addrconf_dad_work+0xc1b/0x14a0 net/ipv6/addrconf.c:-1
process_one_work+0x717/0xc30 kernel/workqueue.c:2302
worker_thread+0xa4d/0x11d0 kernel/workqueue.c:2449
page_owner free stack trace missing
Memory state around the buggy address:
ffff88813469c880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88813469c900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88813469c980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88813469ca00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88813469ca80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
0: 80 3c 2b 00 cmpb $0x0,(%rbx,%rbp,1)
4: 74 08 je 0xe
6: 4c 89 f7 mov %r14,%rdi
9: e8 99 8a 69 00 call 0x698aa7
e: 4d 8b 2e mov (%r14),%r13
11: 4d 85 ed test %r13,%r13
14: 0f 85 cd 00 00 00 jne 0xe7
1a: 4c 89 e7 mov %r12,%rdi
1d: e8 55 98 b3 03 call 0x3b39877
22: fb sti
23: 49 8d 9f 48 0b 00 00 lea 0xb48(%r15),%rbx
* 2a: 48 89 d8 mov %rbx,%rax <-- trapping instruction
2d: 48 c1 e8 03 shr $0x3,%rax
31: 49 bd 00 00 00 00 00 movabs $0xdffffc0000000000,%r13
38: fc ff df
3b: 42 0f b6 04 28 movzbl (%rax,%r13,1),%eax