==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff888132a3fd90 by task syz-executor/1012
CPU: 1 PID: 1012 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
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+0x4bb/0xbc0 kernel/rcu/tree.c:2285
rcu_core+0x5c3/0xe80 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:proc_self_get_link+0xa2/0x180 fs/proc/self.c:22
Code: 49 8b 17 65 48 8b 3d 2d 31 22 7e be 01 00 00 00 e8 a3 76 69 ff 41 89 c4 31 ff 89 c6 e8 f7 44 91 ff 45 85 e4 0f 84 9f 00 00 00 <4d> 85 f6 b8 20 0a 00 00 41 bf c0 0c 00 00 44 0f 44 f8 48 c7 c0 20
RSP: 0018:ffffc90000c07648 EFLAGS: 00000202
RAX: ffffffff81e03ca9 RBX: ffffc90000c07c58 RCX: 0000000000000000
RDX: ffff88811302d100 RSI: 0000000000000008 RDI: 0000000000000000
RBP: ffffc90000c07670 R08: 0000000000000003 R09: 0000000000000004
R10: 0000000000000000 R11: fffff52000180e9a R12: 0000000000000008
R13: dffffc0000000000 R14: 0000000000000000 R15: ffff88812a4fb800
pick_link+0x72e/0xe30 fs/namei.c:1805
step_into+0xc5c/0xf40 fs/namei.c:1875
walk_component fs/namei.c:2011 [inline]
link_path_walk+0x6c1/0xe80 fs/namei.c:2332
path_openat+0x27c/0x2f80 fs/namei.c:3786
do_filp_open+0x1f1/0x430 fs/namei.c:3817
do_sys_openat2+0x15e/0x810 fs/open.c:1343
do_sys_open fs/open.c:1359 [inline]
__do_sys_openat fs/open.c:1375 [inline]
__se_sys_openat fs/open.c:1370 [inline]
__x64_sys_openat+0x136/0x160 fs/open.c:1370
x64_sys_call+0x783/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:258
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: 0033:0x7fb489557fd7
Code: 48 89 fa 4c 89 df e8 a8 56 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:00007ffede8f44b0 EFLAGS: 00000202 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 000055555d52d500 RCX: 00007fb489557fd7
RDX: 0000000000080001 RSI: 00007fb489633d04 RDI: ffffffffffffff9c
RBP: 00007fb489633d04 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000004
R13: 00007ffede8f4570 R14: 000000000000a9ba R15: 00007ffede8f4ae0
Allocated by task 1006:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
kasan_save_alloc_info+0x25/0x30 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+0xb1/0x1e0 mm/slab_common.c:951
kmalloc include/linux/slab.h:568 [inline]
kzalloc include/linux/slab.h:699 [inline]
l2tp_session_create+0x38/0xbe0 net/l2tp/l2tp_core.c:1609
pppol2tp_connect+0xbef/0x1620 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+0x31/0x50 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+0x3f0/0x4e0 net/l2tp/l2tp_core.c:1582
l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1228 [inline]
l2tp_tunnel_del_work+0x1a1/0x410 net/l2tp/l2tp_core.c:1266
process_one_work+0x71f/0xc40 kernel/workqueue.c:2302
worker_thread+0xa29/0x11e0 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/0xf90 kernel/rcu/tree.c:2926
pppol2tp_release+0x208/0x2d0 net/l2tp/l2tp_ppp.c:446
__sock_release net/socket.c:652 [inline]
sock_close+0xf1/0x290 net/socket.c:1389
__fput+0x1fc/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
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
kvfree_call_rcu+0x8b/0x7c0 kernel/rcu/tree.c:3445
inet6_ifa_finish_destroy+0x129/0x1b0 net/ipv6/addrconf.c:1007
in6_ifa_put include/net/addrconf.h:459 [inline]
addrconf_ifdown+0x1265/0x1950 net/ipv6/addrconf.c:3960
addrconf_notify+0x39f/0xe40 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+0x32e/0x4d0 net/core/dev.c:1622
unregister_netdevice_many+0x44f/0x18e0 net/core/dev.c:10979
ip6gre_exit_batch_net+0x5b0/0x600 net/ipv6/ip6_gre.c:1677
ops_exit_list net/core/net_namespace.c:177 [inline]
cleanup_net+0x635/0xb10 net/core/net_namespace.c:604
process_one_work+0x71f/0xc40 kernel/workqueue.c:2302
worker_thread+0xa29/0x11e0 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 ffff888132a3fc00
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
512-byte region [ffff888132a3fc00, ffff888132a3fe00)
The buggy address belongs to the physical page:
page:ffffea0004ca8f00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x132a3c
head:ffffea0004ca8f00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 0000000000000000 dead000000000001 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 0x52a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 289, tgid 289 (syz-executor), ts 23723209866, 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+0x2d12/0x2d80 mm/page_alloc.c:4585
__alloc_pages+0x1fa/0x610 mm/page_alloc.c:5929
alloc_slab_page+0x6e/0xf0 include/linux/gfp.h:-1
allocate_slab mm/slub.c:1967 [inline]
new_slab+0x98/0x3d0 mm/slub.c:2020
___slab_alloc+0x6bd/0xb20 mm/slub.c:3177
__slab_alloc+0x5e/0xa0 mm/slub.c:3263
slab_alloc_node mm/slub.c:3348 [inline]
__kmem_cache_alloc_node+0x203/0x2c0 mm/slub.c:3423
__do_kmalloc_node mm/slab_common.c:937 [inline]
__kmalloc+0xa1/0x1e0 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+0x526/0x1510 net/ipv6/route.c:3796
addrconf_f6i_alloc+0x19c/0x3f0 net/ipv6/route.c:4600
fixup_permanent_addr net/ipv6/addrconf.c:3554 [inline]
addrconf_permanent_addr+0x248/0x960 net/ipv6/addrconf.c:3593
addrconf_notify+0x7cf/0xe40 net/ipv6/addrconf.c:3665
notifier_call_chain kernel/notifier.c:87 [inline]
raw_notifier_call_chain+0xa1/0x110 kernel/notifier.c:455
page_owner free stack trace missing
Memory state around the buggy address:
ffff888132a3fc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888132a3fd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888132a3fd80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888132a3fe00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888132a3fe80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
0: 49 8b 17 mov (%r15),%rdx
3: 65 48 8b 3d 2d 31 22 mov %gs:0x7e22312d(%rip),%rdi # 0x7e223138
a: 7e
b: be 01 00 00 00 mov $0x1,%esi
10: e8 a3 76 69 ff call 0xff6976b8
15: 41 89 c4 mov %eax,%r12d
18: 31 ff xor %edi,%edi
1a: 89 c6 mov %eax,%esi
1c: e8 f7 44 91 ff call 0xff914518
21: 45 85 e4 test %r12d,%r12d
24: 0f 84 9f 00 00 00 je 0xc9
* 2a: 4d 85 f6 test %r14,%r14 <-- trapping instruction
2d: b8 20 0a 00 00 mov $0xa20,%eax
32: 41 bf c0 0c 00 00 mov $0xcc0,%r15d
38: 44 0f 44 f8 cmove %eax,%r15d
3c: 48 rex.W
3d: c7 .byte 0xc7
3e: c0 .byte 0xc0
3f: 20 .byte 0x20