==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff888133b63590 by task syz.1.151/752
CPU: 0 PID: 752 Comm: syz.1.151 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+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:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0x55/0x80 kernel/locking/spinlock.c:194
Code: 80 d3 0d 87 e8 9c 00 b6 fc 4c 89 f7 48 83 3d 11 f4 0c 02 00 74 30 e8 9e 0d 00 00 90 f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 c6 a5 4b fc 65 8b 05 37 8e 01 7b 85 c0 74 05 5b 41 5e 5d c3 e8
RSP: 0018:ffffc90000e0f5e0 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000a06 RCX: dffffc0000000000
RDX: 0000000000000000 RSI: 0000000000000a06 RDI: 0000000000000001
RBP: ffffc90000e0f5f0 R08: ffffea0004e10187 R09: 1ffffd40009c2030
R10: dffffc0000000000 R11: fffff940009c2031 R12: ffffea0004e101c0
R13: ffff888113174e50 R14: dffffc0000000000 R15: 0000000000000288
spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
unlock_page_lruvec_irqrestore include/linux/memcontrol.h:1639 [inline]
release_pages+0x1f4/0xce0 mm/swap.c:1004
free_pages_and_swap_cache+0x86/0xa0 mm/swap_state.c:316
tlb_batch_pages_flush mm/mmu_gather.c:59 [inline]
tlb_flush_mmu_free mm/mmu_gather.c:254 [inline]
tlb_flush_mmu mm/mmu_gather.c:261 [inline]
tlb_finish_mmu+0x1b2/0x380 mm/mmu_gather.c:361
exit_mmap+0x41d/0xc10 mm/mmap.c:3384
__mmput+0x92/0x340 kernel/fork.c:1319
mmput+0x4b/0x150 kernel/fork.c:1343
exit_mm kernel/exit.c:568 [inline]
do_exit+0x9db/0x27c0 kernel/exit.c:873
do_group_exit+0x21b/0x2e0 kernel/exit.c:1029
get_signal+0x1382/0x14f0 kernel/signal.c:2891
arch_do_signal_or_restart+0xd1/0x11c0 arch/x86/kernel/signal.c:871
exit_to_user_mode_loop+0x7a/0xb0 kernel/entry/common.c:174
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
RIP: 0033:0x7f61fef9ce59
Code: Unable to access opcode bytes at 0x7f61fef9ce2f.
RSP: 002b:00007f61ffef10e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: 0000000000000001 RBX: 00007f61ff215fa8 RCX: 00007f61fef9ce59
RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 00007f61ff215fac
RBP: 00007f61ff215fa0 R08: 0007871fd6c42150 R09: 0000000000000000
R10: ffffffffffffffff R11: 0000000000000246 R12: 0000000000000000
R13: 00007f61ff216038 R14: 00007ffda9cdab80 R15: 00007ffda9cdac68
Allocated by task 748:
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
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
The buggy address belongs to the object at ffff888133b63400
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
512-byte region [ffff888133b63400, ffff888133b63600)
The buggy address belongs to the physical page:
page:ffffea0004ced800 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x133b60
head:ffffea0004ced800 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 ffffea0004ced700 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 0x1d2a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 326, tgid 325 (syz.2.9), ts 25314527711, 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_node_track_caller+0xa1/0x1e0 mm/slab_common.c:958
kmalloc_reserve net/core/skbuff.c:449 [inline]
pskb_expand_head+0x1c2/0x12b0 net/core/skbuff.c:1852
skb_ensure_writable+0x2f5/0x490 net/core/skbuff.c:5799
__bpf_try_make_writable net/core/filter.c:1674 [inline]
bpf_try_make_writable net/core/filter.c:1680 [inline]
bpf_try_make_head_writable net/core/filter.c:1688 [inline]
____bpf_clone_redirect net/core/filter.c:2467 [inline]
bpf_clone_redirect+0x1d7/0x4a0 net/core/filter.c:2436
0xffffffffa00006e9
bpf_dispatcher_nop_func include/linux/bpf.h:987 [inline]
__bpf_prog_run include/linux/filter.h:607 [inline]
bpf_prog_run include/linux/filter.h:614 [inline]
bpf_test_run+0x35f/0x940 net/bpf/test_run.c:402
bpf_prog_test_run_skb+0xafb/0x12f0 net/bpf/test_run.c:1191
page_owner free stack trace missing
Memory state around the buggy address:
ffff888133b63480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888133b63500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888133b63580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888133b63600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888133b63680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
0: 80 d3 0d adc $0xd,%bl
3: 87 e8 xchg %ebp,%eax
5: 9c pushf
6: 00 b6 fc 4c 89 f7 add %dh,-0x876b304(%rsi)
c: 48 83 3d 11 f4 0c 02 cmpq $0x0,0x20cf411(%rip) # 0x20cf425
13: 00
14: 74 30 je 0x46
16: e8 9e 0d 00 00 call 0xdb9
1b: 90 nop
1c: f7 c3 00 02 00 00 test $0x200,%ebx
22: 74 01 je 0x25
24: fb sti
25: bf 01 00 00 00 mov $0x1,%edi
* 2a: e8 c6 a5 4b fc call 0xfc4ba5f5 <-- trapping instruction
2f: 65 8b 05 37 8e 01 7b mov %gs:0x7b018e37(%rip),%eax # 0x7b018e6d
36: 85 c0 test %eax,%eax
38: 74 05 je 0x3f
3a: 5b pop %rbx
3b: 41 5e pop %r14
3d: 5d pop %rbp
3e: c3 ret
3f: e8 .byte 0xe8