==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff88811e462d90 by task syz.3.201/861
CPU: 1 PID: 861 Comm: syz.3.201 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
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+0x1dd/0x5f0 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:zap_pte_range mm/memory.c:-1 [inline]
RIP: 0010:zap_pmd_range mm/memory.c:1599 [inline]
RIP: 0010:zap_pud_range mm/memory.c:1628 [inline]
RIP: 0010:zap_p4d_range mm/memory.c:1649 [inline]
RIP: 0010:unmap_page_range+0xb97/0x2360 mm/memory.c:1670
Code: 00 4c 89 2c 24 4c 89 7c 24 30 49 be 00 00 00 00 00 fc ff df 4c 89 fb 48 c1 eb 03 42 80 3c 33 00 74 08 4c 89 ff e8 b9 ef 0b 00 <48> 8b 44 24 30 4c 8b 28 4c 89 ee 48 83 e6 9f 31 ff e8 23 58 c6 ff
RSP: 0018:ffffc900013877a0 EFLAGS: 00000246
RAX: ffffffff81ab3312 RBX: 1ffff1102410a9f7 RCX: ffff88810d24bcc0
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90001387970 R08: ffff88810d24bcc7 R09: 1ffff11021a49798
R10: dffffc0000000000 R11: ffffed1021a49799 R12: 0000200000200000
R13: 0000000000000000 R14: dffffc0000000000 R15: ffff888120854fb8
unmap_single_vma mm/memory.c:1716 [inline]
unmap_vmas+0x34c/0x480 mm/memory.c:1756
exit_mmap+0x2a4/0xc10 mm/mmap.c:3371
__mmput+0x92/0x340 kernel/fork.c:1321
mmput+0x4b/0x150 kernel/fork.c:1345
exit_mm kernel/exit.c:575 [inline]
do_exit+0xa62/0x29f0 kernel/exit.c:883
do_group_exit+0x21b/0x2e0 kernel/exit.c:1040
__do_sys_exit_group kernel/exit.c:1051 [inline]
__se_sys_exit_group kernel/exit.c:1049 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1049
x64_sys_call+0x7b4/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:232
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: 0033:0x7f722e39f559
Code: Unable to access opcode bytes at 0x7f722e39f52f.
RSP: 002b:00007ffd964c40c8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f722e39f559
RDX: 0000000000000064 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007ffd964c412c R08: 0000000000000000 R09: 00000000000927c0
R10: 0000000000000006 R11: 0000000000000246 R12: 0000000000000038
R13: 00000000000927c0 R14: 0000000000008b40 R15: 00007ffd964c4180
Allocated by task 909:
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 451:
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 ffff88811e462c00
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
512-byte region [ffff88811e462c00, ffff88811e462e00)
The buggy address belongs to the physical page:
page:ffffea0004791800 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x11e460
head:ffffea0004791800 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 dead000000000100 dead000000000122 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 142, tgid 142 (dhcpcd), ts 7041216633, 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+0xa2/0x1e0 mm/slab_common.c:945
kmalloc_node include/linux/slab.h:589 [inline]
kzalloc_node include/linux/slab.h:710 [inline]
qdisc_alloc+0x82/0x750 net/sched/sch_generic.c:951
qdisc_create_dflt+0x6b/0x3a0 net/sched/sch_generic.c:1009
attach_default_qdiscs net/sched/sch_generic.c:1195 [inline]
dev_activate+0x152/0x1110 net/sched/sch_generic.c:1249
__dev_open+0x40d/0x520 net/core/dev.c:1518
__dev_change_flags+0x1f2/0x6b0 net/core/dev.c:8693
dev_change_flags+0x80/0x1a0 net/core/dev.c:8764
page_owner free stack trace missing
Memory state around the buggy address:
ffff88811e462c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88811e462d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88811e462d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88811e462e00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88811e462e80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
0: 00 4c 89 2c add %cl,0x2c(%rcx,%rcx,4)
4: 24 4c and $0x4c,%al
6: 89 7c 24 30 mov %edi,0x30(%rsp)
a: 49 be 00 00 00 00 00 movabs $0xdffffc0000000000,%r14
11: fc ff df
14: 4c 89 fb mov %r15,%rbx
17: 48 c1 eb 03 shr $0x3,%rbx
1b: 42 80 3c 33 00 cmpb $0x0,(%rbx,%r14,1)
20: 74 08 je 0x2a
22: 4c 89 ff mov %r15,%rdi
25: e8 b9 ef 0b 00 call 0xbefe3
* 2a: 48 8b 44 24 30 mov 0x30(%rsp),%rax <-- trapping instruction
2f: 4c 8b 28 mov (%rax),%r13
32: 4c 89 ee mov %r13,%rsi
35: 48 83 e6 9f and $0xffffffffffffff9f,%rsi
39: 31 ff xor %edi,%edi
3b: e8 23 58 c6 ff call 0xffc65863