==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff88810e16d990 by task syz.4.6/326
CPU: 1 PID: 326 Comm: syz.4.6 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
__dump_stack+0x21/0x30 lib/dump_stack.c:88
dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
__kasan_report mm/kasan/report.c:427 [inline]
kasan_report+0x10f/0x150 mm/kasan/report.c:444
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:309
rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
rcu_do_batch+0x47d/0xbf0 kernel/rcu/tree.c:2512
rcu_core+0x4a3/0xef0 kernel/rcu/tree.c:2763
rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2776
handle_softirqs+0x250/0x560 kernel/softirq.c:583
__do_softirq kernel/softirq.c:621 [inline]
invoke_softirq kernel/softirq.c:443 [inline]
__irq_exit_rcu+0x52/0xf0 kernel/softirq.c:670
irq_exit_rcu+0x9/0x10 kernel/softirq.c:682
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
sysvec_apic_timer_interrupt+0xa9/0xc0 arch/x86/kernel/apic/apic.c:1108
asm_sysvec_apic_timer_interrupt+0x1b/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:arch_static_branch arch/x86/include/asm/jump_label.h:27 [inline]
RIP: 0010:static_key_false include/linux/jump_label.h:235 [inline]
RIP: 0010:native_write_msr arch/x86/include/asm/msr.h:156 [inline]
RIP: 0010:wrmsrl arch/x86/include/asm/msr.h:271 [inline]
RIP: 0010:native_x2apic_icr_write arch/x86/include/asm/apic.h:241 [inline]
RIP: 0010:__x2apic_send_IPI_dest arch/x86/kernel/apic/x2apic_phys.c:126 [inline]
RIP: 0010:x2apic_send_IPI+0x74/0xc0 arch/x86/kernel/apic/x2apic_phys.c:48
Code: f0 48 c1 e8 03 42 0f b6 04 20 84 c0 75 38 41 0f b7 16 0f ae f0 0f ae e8 83 fb 02 b8 00 04 00 00 0f 45 c3 b9 30 08 00 00 0f 30 <66> 90 5b 41 5c 41 5e 41 5f 5d c3 48 c7 c7 a0 0f 6d 86 4c 89 f6 e8
RSP: 0018:ffffc900078f7918 EFLAGS: 00000206
RAX: 00000000000000fb RBX: 00000000000000fb RCX: 0000000000000830
RDX: 0000000000000000 RSI: 00000000000000fb RDI: 0000000000000000
RBP: ffffc900078f7938 R08: ffff8881f7038ec7 R09: 1ffff1103ee071d8
R10: dffffc0000000000 R11: ffffed103ee071d9 R12: dffffc0000000000
R13: 1ffff92000f1ef38 R14: ffff8881f7021158 R15: ffffffff85e9a840
native_send_call_func_single_ipi+0x5e/0x70 arch/x86/kernel/apic/ipi.c:76
arch_send_call_function_single_ipi arch/x86/include/asm/smp.h:112 [inline]
send_call_function_single_ipi+0xdd/0x180 kernel/sched/core.c:3808
__smp_call_single_queue kernel/smp.c:496 [inline]
generic_exec_single+0x236/0x3a0 kernel/smp.c:529
smp_call_function_single_async+0x81/0x110 kernel/smp.c:803
rdmsr_safe_on_cpu+0x12e/0x260 arch/x86/lib/msr-smp.c:181
msr_read+0x108/0x1b0 arch/x86/kernel/msr.c:67
vfs_read+0x28c/0xc20 fs/read_write.c:483
ksys_read+0x14a/0x260 fs/read_write.c:623
__do_sys_read fs/read_write.c:633 [inline]
__se_sys_read fs/read_write.c:631 [inline]
__x64_sys_read+0x7b/0x90 fs/read_write.c:631
x64_sys_call+0x96d/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:1
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fcb550dd0d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fcb53b36028 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007fcb55364fa0 RCX: 00007fcb550dd0d9
RDX: 0000000000018ff8 RSI: 0000200000019680 RDI: 0000000000000003
RBP: 00007fcb55174024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fcb55365038 R14: 00007fcb55364fa0 R15: 00007fff507bbcc8
Allocated by task 330:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track mm/kasan/common.c:45 [inline]
set_alloc_info mm/kasan/common.c:433 [inline]
____kasan_kmalloc mm/kasan/common.c:512 [inline]
__kasan_kmalloc+0xd4/0x100 mm/kasan/common.c:521
kasan_kmalloc include/linux/kasan.h:227 [inline]
__kmalloc+0x13d/0x2c0 mm/slub.c:4436
kmalloc include/linux/slab.h:624 [inline]
kzalloc include/linux/slab.h:750 [inline]
l2tp_session_create+0x39/0xb60 net/l2tp/l2tp_core.c:1616
pppol2tp_connect+0xbf5/0x1640 net/l2tp/l2tp_ppp.c:772
__sys_connect_file net/socket.c:1923 [inline]
__sys_connect+0x3cb/0x450 net/socket.c:1940
__do_sys_connect net/socket.c:1950 [inline]
__se_sys_connect net/socket.c:1947 [inline]
__x64_sys_connect+0x7a/0x90 net/socket.c:1947
x64_sys_call+0x7c/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:43
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
Freed by task 306:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track+0x4a/0x70 mm/kasan/common.c:45
kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
____kasan_slab_free+0x125/0x160 mm/kasan/common.c:365
__kasan_slab_free+0x11/0x20 mm/kasan/common.c:373
kasan_slab_free include/linux/kasan.h:193 [inline]
slab_free_hook mm/slub.c:1728 [inline]
slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1754
slab_free mm/slub.c:3526 [inline]
kfree+0xc4/0x270 mm/slub.c:4588
l2tp_session_free net/l2tp/l2tp_core.c:168 [inline]
l2tp_session_put+0xaf/0x1a0 net/l2tp/l2tp_core.c:193
l2tp_session_delete+0x3a9/0x4a0 net/l2tp/l2tp_core.c:1589
l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1235 [inline]
l2tp_tunnel_del_work+0x180/0x3d0 net/l2tp/l2tp_core.c:1273
process_one_work+0x6c8/0xbb0 kernel/workqueue.c:2328
worker_thread+0xaa0/0x1250 kernel/workqueue.c:2475
kthread+0x3f5/0x4f0 kernel/kthread.c:337
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
Last potentially related work creation:
kasan_save_stack+0x3a/0x60 mm/kasan/common.c:38
__kasan_record_aux_stack+0xd2/0x100 mm/kasan/generic.c:348
kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358
__call_rcu_common kernel/rcu/tree.c:3011 [inline]
call_rcu+0x10b/0xf60 kernel/rcu/tree.c:3129
pppol2tp_release+0x1e3/0x2b0 net/l2tp/l2tp_ppp.c:447
__sock_release net/socket.c:649 [inline]
sock_close+0xb8/0x200 net/socket.c:1336
__fput+0x22b/0x900 fs/file_table.c:311
____fput+0x15/0x20 fs/file_table.c:339
task_work_run+0x127/0x190 kernel/task_work.c:188
tracehook_notify_resume include/linux/tracehook.h:189 [inline]
exit_to_user_mode_loop+0xd0/0xe0 kernel/entry/common.c:181
exit_to_user_mode_prepare+0x87/0xd0 kernel/entry/common.c:214
__syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:307
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x66/0xd0
The buggy address belongs to the object at ffff88810e16d800
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
512-byte region [ffff88810e16d800, ffff88810e16da00)
The buggy address belongs to the page:
page:ffffea0004385b00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10e16c
head:ffffea0004385b00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 dead000000000100 dead000000000122 ffff888100042f00
raw: 0000000000000000 0000000080100010 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 102, ts 4870906704, free_ts 0
set_page_owner include/linux/page_owner.h:33 [inline]
post_alloc_hook+0x192/0x1b0 mm/page_alloc.c:2607
prep_new_page+0x1c/0x110 mm/page_alloc.c:2613
get_page_from_freelist+0x2c3a/0x2cd0 mm/page_alloc.c:4487
__alloc_pages+0x1a2/0x460 mm/page_alloc.c:5824
alloc_slab_page mm/slub.c:-1 [inline]
allocate_slab mm/slub.c:1937 [inline]
new_slab+0xa0/0x4d0 mm/slub.c:2000
___slab_alloc+0x3ac/0x840 mm/slub.c:3033
__slab_alloc+0x49/0x90 mm/slub.c:3120
slab_alloc_node mm/slub.c:3211 [inline]
slab_alloc mm/slub.c:3255 [inline]
__kmalloc_track_caller+0x169/0x2c0 mm/slub.c:4954
kmalloc_reserve net/core/skbuff.c:357 [inline]
__alloc_skb+0x210/0x730 net/core/skbuff.c:428
alloc_skb include/linux/skbuff.h:1183 [inline]
alloc_uevent_skb+0x85/0x240 lib/kobject_uevent.c:290
uevent_net_broadcast_untagged lib/kobject_uevent.c:326 [inline]
kobject_uevent_net_broadcast+0x335/0x5a0 lib/kobject_uevent.c:409
kobject_uevent_env+0x52b/0x700 lib/kobject_uevent.c:608
kobject_synth_uevent+0x457/0x940 lib/kobject_uevent.c:208
bus_uevent_store+0x4f/0x70 drivers/base/bus.c:765
bus_attr_store+0x79/0xa0 drivers/base/bus.c:124
sysfs_kf_write+0x129/0x150 fs/sysfs/file.c:139
page_owner free stack trace missing
Memory state around the buggy address:
ffff88810e16d880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88810e16d900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88810e16d980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88810e16da00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88810e16da80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
sched: RT throttling activated
----------------
Code disassembly (best guess):
0: f0 48 c1 e8 03 lock shr $0x3,%rax
5: 42 0f b6 04 20 movzbl (%rax,%r12,1),%eax
a: 84 c0 test %al,%al
c: 75 38 jne 0x46
e: 41 0f b7 16 movzwl (%r14),%edx
12: 0f ae f0 mfence
15: 0f ae e8 lfence
18: 83 fb 02 cmp $0x2,%ebx
1b: b8 00 04 00 00 mov $0x400,%eax
20: 0f 45 c3 cmovne %ebx,%eax
23: b9 30 08 00 00 mov $0x830,%ecx
28: 0f 30 wrmsr
* 2a: 66 90 xchg %ax,%ax <-- trapping instruction
2c: 5b pop %rbx
2d: 41 5c pop %r12
2f: 41 5e pop %r14
31: 41 5f pop %r15
33: 5d pop %rbp
34: c3 ret
35: 48 c7 c7 a0 0f 6d 86 mov $0xffffffff866d0fa0,%rdi
3c: 4c 89 f6 mov %r14,%rsi
3f: e8 .byte 0xe8