==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff88812920bd90 by task swapper/0/0
CPU: 0 PID: 0 Comm: swapper/0 Tainted: G W syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
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:default_idle+0xf/0x20 arch/x86/kernel/process.c:730
Code: 8c 4b ff ff ff 4c 89 f7 e8 be c0 f5 fc e9 3e ff ff ff 00 00 cc cc 00 00 cc cc 00 55 48 89 e5 66 90 0f 00 2d 43 02 52 00 fb f4 <5d> c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 48 89 e5 41
RSP: 0018:ffffffff86607d78 EFLAGS: 00000242
RAX: 000000000001ea4c RBX: ffffffff8661c400 RCX: 000000000001ea4c
RDX: 0000000000000001 RSI: ffffffff85637d60 RDI: ffffffff85637d20
RBP: ffffffff86607d78 R08: ffff8881f7038c73 R09: 1ffff1103ee0718e
R10: dffffc0000000000 R11: ffffed103ee0718f R12: 0000000000000000
R13: 1ffffffff0cc3880 R14: dffffc0000000000 R15: dffffc0000000000
arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:721
default_idle_call+0x71/0x1d0 kernel/sched/idle.c:112
cpuidle_idle_call kernel/sched/idle.c:202 [inline]
do_idle+0x368/0x620 kernel/sched/idle.c:326
cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:424
rest_init+0x10a/0x130 init/main.c:756
arch_call_rest_init+0xe/0x10 init/main.c:908
start_kernel+0x46d/0x4e0 init/main.c:1156
x86_64_start_reservations+0x2a/0x30 arch/x86/kernel/head64.c:527
x86_64_start_kernel+0x5b/0x60 arch/x86/kernel/head64.c:508
secondary_startup_64_no_verify+0xb1/0xbb
Allocated by task 1927:
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 45:
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
__call_rcu_common kernel/rcu/tree.c:3011 [inline]
call_rcu+0x10b/0xf60 kernel/rcu/tree.c:3129
fib6_info_release include/net/ip6_fib.h:349 [inline]
fixup_permanent_addr net/ipv6/addrconf.c:3544 [inline]
addrconf_permanent_addr+0x302/0x940 net/ipv6/addrconf.c:3572
addrconf_notify+0x752/0xe00 net/ipv6/addrconf.c:3640
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]
__dev_notify_flags+0x2f4/0x5b0 net/core/dev.c:8925
dev_change_flags+0xe3/0x1a0 net/core/dev.c:8963
do_setlink+0xc95/0x2970 net/core/rtnetlink.c:2782
__rtnl_newlink net/core/rtnetlink.c:3453 [inline]
rtnl_newlink+0x1598/0x1900 net/core/rtnetlink.c:3575
rtnetlink_rcv_msg+0x9fd/0xcb0 net/core/rtnetlink.c:5653
netlink_rcv_skb+0x1e9/0x430 net/netlink/af_netlink.c:2511
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
x64_sys_call+0x178/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:45
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
The buggy address belongs to the object at ffff88812920bc00
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
512-byte region [ffff88812920bc00, ffff88812920be00)
The buggy address belongs to the page:
page:ffffea0004a48200 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x129208
head:ffffea0004a48200 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 ffffea0004307100 0000000300000003 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 0x52a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 286, ts 20576526148, free_ts 0
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+0x16a/0x2c0 mm/slub.c:4432
kmalloc include/linux/slab.h:624 [inline]
kzalloc include/linux/slab.h:750 [inline]
fib6_info_alloc+0x34/0xe0 net/ipv6/ip6_fib.c:155
ip6_route_info_create+0x51b/0x14d0 net/ipv6/route.c:3783
ip6_route_add+0x27/0x130 net/ipv6/route.c:3879
addrconf_prefix_route net/ipv6/addrconf.c:2468 [inline]
fixup_permanent_addr net/ipv6/addrconf.c:3548 [inline]
addrconf_permanent_addr+0x635/0x940 net/ipv6/addrconf.c:3572
addrconf_notify+0x752/0xe00 net/ipv6/addrconf.c:3640
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]
__dev_notify_flags+0x2f4/0x5b0 net/core/dev.c:8925
dev_change_flags+0xe3/0x1a0 net/core/dev.c:8963
page_owner free stack trace missing
Memory state around the buggy address:
ffff88812920bc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88812920bd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88812920bd80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88812920be00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88812920be80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess), 4 bytes skipped:
0: ff 4c 89 f7 decl -0x9(%rcx,%rcx,4)
4: e8 be c0 f5 fc call 0xfcf5c0c7
9: e9 3e ff ff ff jmp 0xffffff4c
e: 00 00 add %al,(%rax)
10: cc int3
11: cc int3
12: 00 00 add %al,(%rax)
14: cc int3
15: cc int3
16: 00 55 48 add %dl,0x48(%rbp)
19: 89 e5 mov %esp,%ebp
1b: 66 90 xchg %ax,%ax
1d: 0f 00 2d 43 02 52 00 verw 0x520243(%rip) # 0x520267
24: fb sti
25: f4 hlt
* 26: 5d pop %rbp <-- trapping instruction
27: c3 ret
28: 66 2e 0f 1f 84 00 00 cs nopw 0x0(%rax,%rax,1)
2f: 00 00 00
32: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)
37: 55 push %rbp
38: 48 89 e5 mov %rsp,%rbp
3b: 41 rex.B