==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff888121411590 by task syz.4.244/921
CPU: 1 PID: 921 Comm: syz.4.244 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:finish_task_switch+0x173/0x7c0 kernel/sched/core.c:5302
Code: 80 3c 2b 00 74 08 4c 89 f7 e8 89 a0 69 00 4d 8b 2e 4d 85 ed 0f 85 cd 00 00 00 4c 89 e7 e8 75 3b b4 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:ffffc900108ffd28 EFLAGS: 00000282
RAX: 0000000080000001 RBX: ffff88811ea67088 RCX: 0000000000000000
RDX: 0000000000000001 RSI: ffffffff85ca6f80 RDI: 00000000ffffffff
RBP: ffffc900108ffd70 R08: ffff888109b90007 R09: 1ffff11021372000
R10: dffffc0000000000 R11: ffffed1021372001 R12: ffff8881f6f37f00
R13: 0000000000000000 R14: ffff8881f6f38a60 R15: ffff88811ea66540
context_switch kernel/sched/core.c:5428 [inline]
__schedule+0xcbb/0x1700 kernel/sched/core.c:6762
schedule+0xbd/0x170 kernel/sched/core.c:6838
exit_to_user_mode_loop+0x51/0xb0 kernel/entry/common.c:165
exit_to_user_mode_prepare+0x87/0xd0 kernel/entry/common.c:210
irqentry_exit_to_user_mode+0x9/0x10 kernel/entry/common.c:316
irqentry_exit+0x12/0x40 kernel/entry/common.c:419
sysvec_apic_timer_interrupt+0x64/0xc0 arch/x86/kernel/apic/apic.c:1118
asm_sysvec_apic_timer_interrupt+0x1b/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0033:0x7fd94fc550fd
Code: c0 08 4c 89 47 28 41 0f b6 14 12 89 47 34 48 d3 e2 49 09 d1 39 f0 7c d5 44 89 ca 29 f0 89 f1 89 47 34 b8 01 00 00 00 49 d3 f9 <48> d3 e0 44 89 4f 30 83 e8 01 21 d0 c3 4c 89 ca eb df 48 83 ec 08
RSP: 002b:00007fd950cad468 EFLAGS: 00000202
RAX: 0000000000000001 RBX: 00007fd950cad530 RCX: 0000000000000000
RDX: 0000000000000055 RSI: 0000000000000000 RDI: 00007fd950cad5d0
RBP: 0000000000000102 R08: 0000000000000001 R09: 0000000000000055
R10: 0000000000000000 R11: 00007fd950cad540 R12: 0000000000000001
R13: 00007fd94fe55b20 R14: 0000000000000000 R15: 00007fd950cad5d0
Allocated by task 918:
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 351:
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_sys_exit kernel/exit.c:1006 [inline]
__se_sys_exit kernel/exit.c:1004 [inline]
__cfi___ia32_sys_exit+0x0/0x10 kernel/exit.c:1004
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
The buggy address belongs to the object at ffff888121411400
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
512-byte region [ffff888121411400, ffff888121411600)
The buggy address belongs to the physical page:
page:ffffea0004850400 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888121413800 pfn:0x121410
head:ffffea0004850400 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 ffffea0004804108 ffffea00042ece08 ffff888100042f00
raw: ffff888121413800 0000000000100003 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 142, tgid 142 (dhcpcd), ts 15944621310, free_ts 0
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
__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]
netlink_alloc_large_skb net/netlink/af_netlink.c:1183 [inline]
netlink_sendmsg+0x635/0xbd0 net/netlink/af_netlink.c:1853
sock_sendmsg_nosec net/socket.c:716 [inline]
__sock_sendmsg net/socket.c:728 [inline]
____sys_sendmsg+0x5fb/0x9c0 net/socket.c:2509
___sys_sendmsg+0x2a2/0x360 net/socket.c:2563
__sys_sendmsg net/socket.c:2592 [inline]
__do_sys_sendmsg net/socket.c:2601 [inline]
__se_sys_sendmsg net/socket.c:2599 [inline]
__x64_sys_sendmsg+0x20d/0x2e0 net/socket.c:2599
x64_sys_call+0x171/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:47
page_owner free stack trace missing
Memory state around the buggy address:
ffff888121411480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888121411500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888121411580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888121411600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888121411680: 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 89 a0 69 00 call 0x69a097
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 75 3b b4 03 call 0x3b43b97
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