==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff888129a5d590 by task rcu_preempt/14
CPU: 0 PID: 14 Comm: rcu_preempt 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_irq include/linux/spinlock_api_smp.h:160 [inline]
RIP: 0010:_raw_spin_unlock_irq+0x48/0x70 kernel/locking/spinlock.c:202
Code: 74 12 48 89 fb 48 c7 c7 80 d3 0d 87 e8 11 00 b6 fc 48 89 df 48 83 3d 86 f3 0c 02 00 74 26 e8 13 0d 00 00 90 fb bf 01 00 00 00 43 a5 4b fc 65 8b 05 b4 8d 01 7b 85 c0 74 03 5b 5d c3 e8 84 9c
RSP: 0018:ffffc900000e7d08 EFLAGS: 00000246
RAX: 0000000000000001 RBX: ffffffff871b3e88 RCX: dffffc0000000000
RDX: dffffc0000000000 RSI: ffffffff85ca61c0 RDI: 0000000000000001
RBP: ffffc900000e7d10 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff5200001cf90 R12: 0000000000000000
R13: dffffc0000000000 R14: fffffffffffffffc R15: 0000000000000000
rcu_gp_init+0xc06/0xf30 kernel/rcu/tree.c:1599
rcu_gp_kthread+0x18e/0x390 kernel/rcu/tree.c:1895
kthread+0x281/0x320 kernel/kthread.c:386
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
Allocated by task 9040:
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 703:
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 ffff888129a5d400
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
512-byte region [ffff888129a5d400, ffff888129a5d600)
The buggy address belongs to the physical page:
page:ffffea0004a69700 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x129a5c
head:ffffea0004a69700 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 ffffea0004a69600 dead000000000003 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 8629, tgid 8628 (syz.3.2963), ts 443542300097, free_ts 440366244766
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
0xffffffffa00009ed
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 last free stack trace:
reset_page_owner include/linux/page_owner.h:26 [inline]
free_pages_prepare mm/page_alloc.c:1580 [inline]
free_pcp_prepare mm/page_alloc.c:1654 [inline]
free_unref_page_prepare+0x80c/0x820 mm/page_alloc.c:3621
free_unref_page+0x93/0x530 mm/page_alloc.c:3719
free_the_page mm/page_alloc.c:863 [inline]
__free_pages+0x67/0x100 mm/page_alloc.c:6020
__free_slab+0xc7/0x1a0 mm/slub.c:2044
free_slab mm/slub.c:2059 [inline]
discard_slab mm/slub.c:2065 [inline]
__unfreeze_partials+0x15a/0x190 mm/slub.c:2614
put_cpu_partial+0xa9/0x100 mm/slub.c:2690
__slab_free+0x1c4/0x280 mm/slub.c:3589
do_slab_free mm/slub.c:3666 [inline]
___cache_free+0xbf/0xd0 mm/slub.c:3722
qlink_free mm/kasan/quarantine.c:168 [inline]
qlist_free_all+0xc6/0x140 mm/kasan/quarantine.c:187
kasan_quarantine_reduce+0x14a/0x170 mm/kasan/quarantine.c:294
__kasan_slab_alloc+0x24/0x80 mm/kasan/common.c:311
kasan_slab_alloc include/linux/kasan.h:202 [inline]
slab_post_alloc_hook+0x4f/0x2d0 mm/slab.h:768
slab_alloc_node mm/slub.c:3382 [inline]
slab_alloc mm/slub.c:3392 [inline]
__kmem_cache_alloc_lru mm/slub.c:3399 [inline]
kmem_cache_alloc+0x166/0x320 mm/slub.c:3408
kmem_cache_zalloc include/linux/slab.h:689 [inline]
lsm_file_alloc security/security.c:576 [inline]
security_file_alloc+0x33/0x130 security/security.c:1544
__alloc_file+0xb5/0x2a0 fs/file_table.c:143
alloc_empty_file+0x97/0x180 fs/file_table.c:187
Memory state around the buggy address:
ffff888129a5d480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888129a5d500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888129a5d580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888129a5d600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888129a5d680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
0: 74 12 je 0x14
2: 48 89 fb mov %rdi,%rbx
5: 48 c7 c7 80 d3 0d 87 mov $0xffffffff870dd380,%rdi
c: e8 11 00 b6 fc call 0xfcb60022
11: 48 89 df mov %rbx,%rdi
14: 48 83 3d 86 f3 0c 02 cmpq $0x0,0x20cf386(%rip) # 0x20cf3a2
1b: 00
1c: 74 26 je 0x44
1e: e8 13 0d 00 00 call 0xd36
23: 90 nop
24: fb sti
25: bf 01 00 00 00 mov $0x1,%edi
* 2a: e8 43 a5 4b fc call 0xfc4ba572 <-- trapping instruction
2f: 65 8b 05 b4 8d 01 7b mov %gs:0x7b018db4(%rip),%eax # 0x7b018dea
36: 85 c0 test %eax,%eax
38: 74 03 je 0x3d
3a: 5b pop %rbx
3b: 5d pop %rbp
3c: c3 ret
3d: e8 .byte 0xe8
3e: 84 .byte 0x84
3f: 9c pushf