==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff888117869d90 by task syz.1.69/582
CPU: 1 PID: 582 Comm: syz.1.69 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
Call Trace:
__dump_stack+0x21/0x24 lib/dump_stack.c:77
dump_stack_lvl+0x1a7/0x208 lib/dump_stack.c:118
print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
__kasan_report mm/kasan/report.c:435 [inline]
kasan_report+0x100/0x140 mm/kasan/report.c:452
__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+0x448/0xaf0 kernel/rcu/tree.c:2484
rcu_core+0x50a/0xca0 kernel/rcu/tree.c:2735
rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2748
__do_softirq+0x255/0x563 kernel/softirq.c:309
asm_call_irq_on_stack+0xf/0x20
__run_on_irqstack arch/x86/include/asm/irq_stack.h:26 [inline]
run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:77 [inline]
do_softirq_own_stack+0x60/0x80 arch/x86/kernel/irq_64.c:77
invoke_softirq kernel/softirq.c:405 [inline]
__irq_exit_rcu+0x128/0x150 kernel/softirq.c:435
irq_exit_rcu+0x9/0x10 kernel/softirq.c:447
sysvec_apic_timer_interrupt+0xbf/0xe0 arch/x86/kernel/apic/apic.c:1106
asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:635
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0x51/0x80 kernel/locking/spinlock.c:191
Code: 89 fe 48 c7 c7 70 73 4c 86 e8 1b c0 1c fd 4c 89 f7 48 83 3d 60 f6 c9 01 00 74 34 e8 5d 5d c9 fc 66 90 48 89 5d e8 ff 75 e8 9d 01 00 00 00 e8 75 56 c2 fc 65 8b 05 5a f0 7f 7b 85 c0 74 09 48
RSP: 0018:ffffc90002ab75f0 EFLAGS: 00000a06
RAX: 0000000000000001 RBX: 0000000000000a06 RCX: dffffc0000000000
RDX: 0000000000000001 RSI: 0000000000000a06 RDI: ffff888115c54900
RBP: ffffc90002ab7608 R08: ffff8881181be417 R09: 1ffff11023037c82
R10: dffffc0000000000 R11: ffffed1023037c83 R12: ffff888115c54908
R13: 1ffff92000556edb R14: ffff8881181be400 R15: 0000000000000001
spin_unlock_irqrestore include/linux/spinlock.h:410 [inline]
prepare_to_wait_exclusive+0x1b9/0x1f0 kernel/sched/wait.c:277
unix_wait_for_peer+0x105/0x2e0 net/unix/af_unix.c:1220
unix_dgram_sendmsg+0x10fc/0x18f0 net/unix/af_unix.c:1818
sock_sendmsg_nosec net/socket.c:652 [inline]
__sock_sendmsg net/socket.c:664 [inline]
____sys_sendmsg+0x5be/0x8f0 net/socket.c:2377
___sys_sendmsg+0x236/0x2e0 net/socket.c:2431
__sys_sendmmsg+0x2ab/0x4c0 net/socket.c:2517
__do_sys_sendmmsg net/socket.c:2546 [inline]
__se_sys_sendmmsg net/socket.c:2543 [inline]
__x64_sys_sendmmsg+0xa0/0xb0 net/socket.c:2543
do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f21c7e75199
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:00007f21c68ce028 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007f21c80fcfa0 RCX: 00007f21c7e75199
RDX: 0000000000000651 RSI: 0000200000000000 RDI: 0000000000000007
RBP: 00007f21c7f0c888 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f21c80fd038 R14: 00007f21c80fcfa0 R15: 00007ffc3fcc3998
Allocated by task 590:
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:430 [inline]
____kasan_kmalloc mm/kasan/common.c:509 [inline]
__kasan_kmalloc+0xd4/0x100 mm/kasan/common.c:518
kasan_kmalloc include/linux/kasan.h:254 [inline]
__kmalloc+0x19f/0x330 mm/slub.c:4038
kmalloc include/linux/slab.h:560 [inline]
kzalloc include/linux/slab.h:667 [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:1867 [inline]
__sys_connect+0x3ce/0x450 net/socket.c:1884
__do_sys_connect net/socket.c:1894 [inline]
__se_sys_connect net/socket.c:1891 [inline]
__x64_sys_connect+0x7a/0x90 net/socket.c:1891
do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x61/0xcb
Freed by task 300:
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:362
__kasan_slab_free+0x11/0x20 mm/kasan/common.c:370
kasan_slab_free include/linux/kasan.h:220 [inline]
slab_free_hook mm/slub.c:1600 [inline]
slab_free_freelist_hook+0xc5/0x190 mm/slub.c:1626
slab_free mm/slub.c:3208 [inline]
kfree+0xc0/0x270 mm/slub.c:4196
l2tp_session_free net/l2tp/l2tp_core.c:168 [inline]
l2tp_session_put+0xb2/0x1a0 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+0x6fd/0xbc0 kernel/workqueue.c:2301
worker_thread+0xa8e/0x13c0 kernel/workqueue.c:2447
kthread+0x324/0x3b0 kernel/kthread.c:313
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298
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 kernel/rcu/tree.c:2980 [inline]
call_rcu+0x11a/0x1090 kernel/rcu/tree.c:3054
pppol2tp_release+0x1e3/0x2b0 net/l2tp/l2tp_ppp.c:447
__sock_release net/socket.c:597 [inline]
sock_close+0xb8/0x200 net/socket.c:1287
__fput+0x2dc/0x730 fs/file_table.c:281
____fput+0x15/0x20 fs/file_table.c:314
task_work_run+0x127/0x190 kernel/task_work.c:189
tracehook_notify_resume include/linux/tracehook.h:188 [inline]
exit_to_user_mode_loop+0xcb/0xe0 kernel/entry/common.c:175
exit_to_user_mode_prepare+0x76/0xa0 kernel/entry/common.c:202
syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:277
do_syscall_64+0x3d/0x40 arch/x86/entry/common.c:56
entry_SYSCALL_64_after_hwframe+0x61/0xcb
The buggy address belongs to the object at ffff888117869c00
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
512-byte region [ffff888117869c00, ffff888117869e00)
The buggy address belongs to the page:
page:ffffea00045e1a00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x117868
head:ffffea00045e1a00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 0000000000000000 0000000100000001 ffff888100043080
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 104, ts 4485646383, free_ts 0
set_page_owner include/linux/page_owner.h:35 [inline]
post_alloc_hook mm/page_alloc.c:2456 [inline]
prep_new_page+0x176/0x190 mm/page_alloc.c:2462
get_page_from_freelist+0x225f/0x23f0 mm/page_alloc.c:4254
__alloc_pages_nodemask+0x29a/0x640 mm/page_alloc.c:5384
alloc_slab_page mm/slub.c:-1 [inline]
allocate_slab mm/slub.c:1813 [inline]
new_slab+0x84/0x3f0 mm/slub.c:1874
new_slab_objects mm/slub.c:2632 [inline]
___slab_alloc+0x2f8/0x4c0 mm/slub.c:2796
__slab_alloc+0x63/0xa0 mm/slub.c:2836
slab_alloc_node mm/slub.c:2918 [inline]
slab_alloc mm/slub.c:2960 [inline]
__kmalloc_track_caller+0x1e4/0x310 mm/slub.c:4541
__kmalloc_reserve net/core/skbuff.c:144 [inline]
__alloc_skb+0xdc/0x520 net/core/skbuff.c:212
alloc_skb include/linux/skbuff.h:1126 [inline]
alloc_skb_with_frags+0xa3/0x560 net/core/skbuff.c:6048
sock_alloc_send_pskb+0x87f/0x9a0 net/core/sock.c:2392
unix_dgram_sendmsg+0x6f3/0x18f0 net/unix/af_unix.c:1725
sock_sendmsg_nosec net/socket.c:652 [inline]
__sock_sendmsg net/socket.c:664 [inline]
sock_write_iter+0x2a6/0x3a0 net/socket.c:1019
call_write_iter include/linux/fs.h:2072 [inline]
new_sync_write fs/read_write.c:518 [inline]
vfs_write+0x770/0xd70 fs/read_write.c:605
ksys_write+0x14a/0x260 fs/read_write.c:658
__do_sys_write fs/read_write.c:670 [inline]
__se_sys_write fs/read_write.c:667 [inline]
__x64_sys_write+0x7b/0x90 fs/read_write.c:667
do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
page_owner free stack trace missing
Memory state around the buggy address:
ffff888117869c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888117869d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888117869d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888117869e00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888117869e80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
0: 89 fe mov %edi,%esi
2: 48 c7 c7 70 73 4c 86 mov $0xffffffff864c7370,%rdi
9: e8 1b c0 1c fd call 0xfd1cc029
e: 4c 89 f7 mov %r14,%rdi
11: 48 83 3d 60 f6 c9 01 cmpq $0x0,0x1c9f660(%rip) # 0x1c9f679
18: 00
19: 74 34 je 0x4f
1b: e8 5d 5d c9 fc call 0xfcc95d7d
20: 66 90 xchg %ax,%ax
22: 48 89 5d e8 mov %rbx,-0x18(%rbp)
26: ff 75 e8 push -0x18(%rbp)
29: 9d popf
* 2a: bf 01 00 00 00 mov $0x1,%edi <-- trapping instruction
2f: e8 75 56 c2 fc call 0xfcc256a9
34: 65 8b 05 5a f0 7f 7b mov %gs:0x7b7ff05a(%rip),%eax # 0x7b7ff095
3b: 85 c0 test %eax,%eax
3d: 74 09 je 0x48
3f: 48 rex.W