==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff88810ff75d90 by task swapper/0/0
CPU: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
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:default_idle+0xf/0x20 arch/x86/kernel/process.c:742
Code: cc 00 00 cc cc 00 00 cc cc 00 00 90 90 90 90 90 90 90 90 90 90 90 b8 0c 67 40 a5 55 48 89 e5 66 90 0f 00 2d 03 d9 64 00 fb f4 <5d> c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 90 90 90 90 90
RSP: 0018:ffffffff87007d58 EFLAGS: 00000257
RAX: ffff8881f6e00000 RBX: ffffffff8701c680 RCX: eda1a01ee884f500
RDX: 0000000000000001 RSI: ffffffff85ca6fc0 RDI: ffffffff85ca6f80
RBP: ffffffff87007d58 R08: ffff8881f6e348b3 R09: 1ffff1103edc6916
R10: 0000000000000000 R11: ffffffff85015710 R12: dffffc0000000000
R13: 0000000000000000 R14: ffffffff8701c680 R15: dffffc0000000000
arch_cpu_idle+0x1c/0x20 arch/x86/kernel/process.c:733
default_idle_call+0x71/0x1d0 kernel/sched/idle.c:109
cpuidle_idle_call kernel/sched/idle.c:199 [inline]
do_idle+0x354/0x640 kernel/sched/idle.c:323
cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:422
rest_init+0x10a/0x130 init/main.c:744
arch_call_rest_init+0xe/0x10 init/main.c:904
start_kernel+0x483/0x4f1 init/main.c:1275
x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:555
x86_64_start_kernel+0x7c/0x81 arch/x86/kernel/head64.c:536
secondary_startup_64_no_verify+0xce/0xdb
Allocated by task 374:
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:1614
pppol2tp_connect+0xbf5/0x1640 net/l2tp/l2tp_ppp.c:771
__sys_connect_file net/socket.c:2001 [inline]
__sys_connect+0x3da/0x460 net/socket.c:2018
__do_sys_connect net/socket.c:2028 [inline]
__se_sys_connect net/socket.c:2025 [inline]
__x64_sys_connect+0x7a/0x90 net/socket.c:2025
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 8:
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:1587
l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1233 [inline]
l2tp_tunnel_del_work+0x199/0x410 net/l2tp/l2tp_core.c:1271
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:1390
__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+0xb0d/0x29f0 kernel/exit.c:896
do_group_exit+0x21b/0x2e0 kernel/exit.c:1040
get_signal+0x167c/0x1700 kernel/signal.c:2904
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 ffff88810ff75c00
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
512-byte region [ffff88810ff75c00, ffff88810ff75e00)
The buggy address belongs to the physical page:
page:ffffea00043fdd00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10ff74
head:ffffea00043fdd00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 0000000000000000 dead000000000122 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 369, tgid 369 (syz-executor), ts 28898432676, free_ts 27924831112
set_page_owner include/linux/page_owner.h:33 [inline]
post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2673
prep_new_page+0x1c/0x110 mm/page_alloc.c:2680
get_page_from_freelist+0x2ca9/0x2d20 mm/page_alloc.c:4587
__alloc_pages+0x1fa/0x610 mm/page_alloc.c:5931
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
kmalloc_node_trace+0x26/0xb0 mm/slab_common.c:1041
kmalloc_node include/linux/slab.h:585 [inline]
kzalloc_node include/linux/slab.h:710 [inline]
alloc_fair_sched_group+0x218/0x6f0 kernel/sched/fair.c:12340
sched_create_group+0x42/0x230 kernel/sched/core.c:10454
cpu_cgroup_css_alloc+0x18/0x1c0 kernel/sched/core.c:10605
css_create kernel/cgroup/cgroup.c:5623 [inline]
cgroup_apply_control_enable+0x38d/0xdd0 kernel/cgroup/cgroup.c:3315
cgroup_mkdir+0x12f6/0x1550 kernel/cgroup/cgroup.c:5842
kernfs_iop_mkdir+0x1b1/0x2b0 fs/kernfs/dir.c:1221
page last free stack trace:
reset_page_owner include/linux/page_owner.h:26 [inline]
free_pages_prepare mm/page_alloc.c:1581 [inline]
free_pcp_prepare mm/page_alloc.c:1655 [inline]
free_unref_page_prepare+0x81b/0x820 mm/page_alloc.c:3622
free_unref_page+0x93/0x530 mm/page_alloc.c:3720
free_the_page mm/page_alloc.c:863 [inline]
__free_pages+0x67/0x100 mm/page_alloc.c:6021
__vunmap+0xa3c/0xc00 mm/vmalloc.c:2739
__vfree mm/vmalloc.c:2788 [inline]
vfree+0x61/0x90 mm/vmalloc.c:2819
kcov_put kernel/kcov.c:437 [inline]
kcov_close+0x2b/0x50 kernel/kcov.c:533
__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+0xb0d/0x29f0 kernel/exit.c:896
do_group_exit+0x21b/0x2e0 kernel/exit.c:1040
get_signal+0x167c/0x1700 kernel/signal.c:2904
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
Memory state around the buggy address:
ffff88810ff75c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88810ff75d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88810ff75d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88810ff75e00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88810ff75e80: fc fc fc f
----------------
Code disassembly (best guess):
0: cc int3
1: 00 00 add %al,(%rax)
3: cc int3
4: cc int3
5: 00 00 add %al,(%rax)
7: cc int3
8: cc int3
9: 00 00 add %al,(%rax)
b: 90 nop
c: 90 nop
d: 90 nop
e: 90 nop
f: 90 nop
10: 90 nop
11: 90 nop
12: 90 nop
13: 90 nop
14: 90 nop
15: 90 nop
16: b8 0c 67 40 a5 mov $0xa540670c,%eax
1b: 55 push %rbp
1c: 48 89 e5 mov %rsp,%rbp
1f: 66 90 xchg %ax,%ax
21: 0f 00 2d 03 d9 64 00 verw 0x64d903(%rip) # 0x64d92b
28: fb sti
29: f4 hlt
* 2a: 5d pop %rbp <-- trapping instruction
2b: c3 ret
2c: 66 2e 0f 1f 84 00 00 cs nopw 0x0(%rax,%rax,1)
33: 00 00 00
36: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)
3b: 90 nop
3c: 90 nop
3d: 90 nop
3e: 90 nop
3f: 90 nop