==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff888132fdb990 by task syz.5.335/1643
CPU: 1 PID: 1643 Comm: syz.5.335 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+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:pmd_read_atomic include/linux/pgtable.h:1352 [inline]
RIP: 0010:pmd_none_or_trans_huge_or_clear_bad include/linux/pgtable.h:1382 [inline]
RIP: 0010:pmd_trans_unstable include/linux/pgtable.h:1440 [inline]
RIP: 0010:do_anonymous_page mm/memory.c:4258 [inline]
RIP: 0010:handle_pte_fault mm/memory.c:5181 [inline]
RIP: 0010:__handle_mm_fault mm/memory.c:5325 [inline]
RIP: 0010:handle_mm_fault+0x1401/0x26b0 mm/memory.c:5465
Code: 9f 0f 84 25 0f 00 00 e8 2d 91 c5 ff 4c 8b b4 24 10 01 00 00 4c 89 f0 48 c1 e8 03 42 80 3c 28 00 74 08 4c 89 f7 e8 bf 1b 0b 00 <4d> 8b 2e 4c 89 ee 48 83 e6 9f 31 db 31 ff e8 bc 95 c5 ff 4c 89 e8
RSP: 0000:ffffc9000a0e7c80 EFLAGS: 00000246
RAX: 1ffff110220e90e0 RBX: ffff888110748700 RCX: ffff88811c221440
RDX: 0000000000000000 RSI: 000000013e642007 RDI: 0000000000000000
RBP: ffffc9000a0e7e50 R08: ffffc9000a0e7dcf R09: ffffc9000a0e7d8c
R10: dffffc0000000000 R11: fffff5200141cfba R12: ffff88813e9c9b78
R13: dffffc0000000000 R14: ffff888110748700 R15: ffff88813e9c9b58
do_user_addr_fault+0x900/0x1030 arch/x86/mm/fault.c:1321
handle_page_fault arch/x86/mm/fault.c:1464 [inline]
exc_page_fault+0x51/0xb0 arch/x86/mm/fault.c:1517
asm_exc_page_fault+0x27/0x30 arch/x86/include/asm/idtentry.h:608
RIP: 0033:0x7ff11bc517bf
Code: 1f 84 00 00 00 00 00 0f 1f 40 00 41 89 fb 44 8d 56 04 4c 8d 0d 52 08 3c 00 89 f0 4c 8d 05 49 e8 3b 00 89 c2 81 e2 ff 1f 00 00 <49> 8b 0c d1 48 39 f1 74 28 48 85 c9 74 29 45 38 1c 10 75 23 83 c0
RSP: 002b:00007ffef3d2fc38 EFLAGS: 00010206
RAX: 0000000084ee1359 RBX: ffffffff84ee1359 RCX: 0000000000000003
RDX: 0000000000001359 RSI: ffffffff84ee1359 RDI: 0000000000000000
RBP: 0000000000000000 R08: 00007ff11c010000 R09: 00007ff11c012000
R10: 0000000084ee135d R11: 0000000000000000 R12: 00007ff11c026038
R13: 000000000000000b R14: ffffffff84ee13d6 R15: 00007ff11cb55720
Allocated by task 1625:
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 43:
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
The buggy address belongs to the object at ffff888132fdb800
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
512-byte region [ffff888132fdb800, ffff888132fdba00)
The buggy address belongs to the physical page:
page:ffffea0004cbf600 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x132fd8
head:ffffea0004cbf600 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 ffffea00043fa000 dead000000000002 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 289, tgid 289 (syz-executor), ts 25353337133, 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
inet6_addr_add+0x1a8/0x9c0 net/ipv6/addrconf.c:3007
inet6_rtm_newaddr+0x74a/0xa10 net/ipv6/addrconf.c:4999
page_owner free stack trace missing
Memory state around the buggy address:
ffff888132fdb880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888132fdb900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888132fdb980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888132fdba00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888132fdba80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
0: 9f lahf
1: 0f 84 25 0f 00 00 je 0xf2c
7: e8 2d 91 c5 ff call 0xffc59139
c: 4c 8b b4 24 10 01 00 mov 0x110(%rsp),%r14
13: 00
14: 4c 89 f0 mov %r14,%rax
17: 48 c1 e8 03 shr $0x3,%rax
1b: 42 80 3c 28 00 cmpb $0x0,(%rax,%r13,1)
20: 74 08 je 0x2a
22: 4c 89 f7 mov %r14,%rdi
25: e8 bf 1b 0b 00 call 0xb1be9
* 2a: 4d 8b 2e mov (%r14),%r13 <-- trapping instruction
2d: 4c 89 ee mov %r13,%rsi
30: 48 83 e6 9f and $0xffffffffffffff9f,%rsi
34: 31 db xor %ebx,%ebx
36: 31 ff xor %edi,%edi
38: e8 bc 95 c5 ff call 0xffc595f9
3d: 4c 89 e8 mov %r13,%rax