==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff888132dba990 by task udevd/4648
CPU: 1 PID: 4648 Comm: udevd 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+0x40d/0xc30 kernel/rcu/tree.c:2283
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:check_kcov_mode kernel/kcov.c:193 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x36/0x60 kernel/kcov.c:216
Code: 70 07 91 7e 65 8b 15 71 07 91 7e 81 e2 00 01 ff 00 74 11 81 fa 00 01 00 00 75 35 83 b9 6c 0b 00 00 00 74 2c 8b 91 48 0b 00 00 <83> fa 02 75 21 48 8b 91 50 0b 00 00 48 8b 32 48 8d 7e 01 8b 89 4c
RSP: 0018:ffffc900009e7950 EFLAGS: 00000246
RAX: ffffffff81007b4f RBX: 0000000000000000 RCX: ffff88813245e540
RDX: 0000000000000000 RSI: ffffffff852000cc RDI: 0000000000000000
RBP: ffffc900009e7950 R08: ffffc900009e7ab0 R09: ffffc900009e7aa8
R10: 000000000000000a R11: fffff5200013cf49 R12: ffff88813245e540
R13: dffffc0000000000 R14: 0000000000000001 R15: 1ffff9200013cf46
in_gate_area_no_mm+0xf/0x60 arch/x86/entry/vsyscall/vsyscall_64.c:331
is_kernel_text include/linux/kallsyms.h:31 [inline]
core_kernel_text kernel/extable.c:68 [inline]
kernel_text_address+0x2f/0xd0 kernel/extable.c:99
__kernel_text_address+0xd/0x30 kernel/extable.c:79
unwind_get_return_address+0x4d/0x90 arch/x86/kernel/unwind_frame.c:19
arch_stack_walk+0xfc/0x150 arch/x86/kernel/stacktrace.c:26
stack_trace_save+0xa6/0xf0 kernel/stacktrace.c:122
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+0xe/0x10 mm/kasan/generic.c:491
task_work_add+0x7f/0x330 kernel/task_work.c:48
fput+0xe1/0x1a0 fs/file_table.c:376
filp_close+0x111/0x160 fs/open.c:1462
close_fd+0x7a/0x90 fs/file.c:668
__do_sys_close fs/open.c:1475 [inline]
__se_sys_close fs/open.c:1473 [inline]
__x64_sys_close+0x39/0x80 fs/open.c:1473
x64_sys_call+0x8f6/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:4
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: 0033:0x7f05ae4a7407
Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007ffdf31a1580 EFLAGS: 00000202 ORIG_RAX: 0000000000000003
RAX: ffffffffffffffda RBX: 00007f05aec2c880 RCX: 00007f05ae4a7407
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000000000b
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000
R13: 00007ffdf31a1620 R14: 0000000000000000 R15: 0000000000000009
Allocated by task 5042:
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 1443:
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_sys_exit kernel/exit.c:996 [inline]
__se_sys_exit kernel/exit.c:994 [inline]
__cfi___ia32_sys_exit+0x0/0x10 kernel/exit.c:994
x64_sys_call+0x67/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:61
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
Second to 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
fib6_info_release include/net/ip6_fib.h:350 [inline]
__ip6_del_rt+0xf5/0x150 net/ipv6/route.c:3919
ip6_del_rt+0xbe/0x110 net/ipv6/route.c:3930
__ipv6_ifa_notify+0x877/0xe80 net/ipv6/addrconf.c:6267
addrconf_ifdown+0xdfd/0x1950 net/ipv6/addrconf.c:3948
addrconf_notify+0x39f/0xe30 net/ipv6/addrconf.c:-1
notifier_call_chain kernel/notifier.c:87 [inline]
raw_notifier_call_chain+0xa1/0x110 kernel/notifier.c:455
call_netdevice_notifiers_info net/core/dev.c:2022 [inline]
call_netdevice_notifiers_extack net/core/dev.c:2060 [inline]
call_netdevice_notifiers net/core/dev.c:2074 [inline]
dev_close_many+0x325/0x4d0 net/core/dev.c:1622
unregister_netdevice_many+0x43f/0x1910 net/core/dev.c:10979
default_device_exit_batch+0x951/0x9f0 net/core/dev.c:11518
ops_exit_list net/core/net_namespace.c:177 [inline]
cleanup_net+0x630/0xb10 net/core/net_namespace.c:604
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
The buggy address belongs to the object at ffff888132dba800
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
512-byte region [ffff888132dba800, ffff888132dbaa00)
The buggy address belongs to the physical page:
page:ffffea0004cb6e00 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888132db8800 pfn:0x132db8
head:ffffea0004cb6e00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 ffffea00047b9e00 dead000000000002 ffff888100042f00
raw: ffff888132db8800 000000008010000c 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 43, tgid 43 (kworker/u4:2), ts 25618333155, 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+0xa4/0x1e0 mm/slab_common.c:951
kmalloc include/linux/slab.h:568 [inline]
kzalloc include/linux/slab.h:699 [inline]
fib6_info_alloc+0x34/0xe0 net/ipv6/ip6_fib.c:156
ip6_route_info_create+0x51b/0x14d0 net/ipv6/route.c:3796
ip6_route_add+0x27/0x130 net/ipv6/route.c:3892
addrconf_add_mroute net/ipv6/addrconf.c:2530 [inline]
addrconf_add_dev+0x388/0x4a0 net/ipv6/addrconf.c:2548
addrconf_dev_config net/ipv6/addrconf.c:3450 [inline]
addrconf_init_auto_addrs+0x7b9/0xbc0 net/ipv6/addrconf.c:3538
addrconf_notify+0x7fe/0xe30 net/ipv6/addrconf.c:3711
page_owner free stack trace missing
Memory state around the buggy address:
ffff888132dba880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888132dba900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888132dba980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888132dbaa00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888132dbaa80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
0: 70 07 jo 0x9
2: 91 xchg %eax,%ecx
3: 7e 65 jle 0x6a
5: 8b 15 71 07 91 7e mov 0x7e910771(%rip),%edx # 0x7e91077c
b: 81 e2 00 01 ff 00 and $0xff0100,%edx
11: 74 11 je 0x24
13: 81 fa 00 01 00 00 cmp $0x100,%edx
19: 75 35 jne 0x50
1b: 83 b9 6c 0b 00 00 00 cmpl $0x0,0xb6c(%rcx)
22: 74 2c je 0x50
24: 8b 91 48 0b 00 00 mov 0xb48(%rcx),%edx
* 2a: 83 fa 02 cmp $0x2,%edx <-- trapping instruction
2d: 75 21 jne 0x50
2f: 48 8b 91 50 0b 00 00 mov 0xb50(%rcx),%rdx
36: 48 8b 32 mov (%rdx),%rsi
39: 48 8d 7e 01 lea 0x1(%rsi),%rdi
3d: 8b .byte 0x8b
3e: 89 .byte 0x89
3f: 4c rex.WR