==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff888118cd7990 by task syz.3.53/456
CPU: 0 PID: 456 Comm: syz.3.53 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
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:arch_atomic64_read arch/x86/include/asm/atomic64_64.h:22 [inline]
RIP: 0010:arch_atomic_long_read include/linux/atomic/atomic-long.h:29 [inline]
RIP: 0010:atomic_long_read include/linux/atomic/atomic-instrumented.h:1266 [inline]
RIP: 0010:__mutex_owner kernel/locking/mutex.c:86 [inline]
RIP: 0010:mutex_spin_on_owner+0x2e1/0x450 kernel/locking/mutex.c:371
Code: 3c 34 00 74 08 4c 89 ef e8 3c ae 61 00 49 f7 45 00 01 00 00 00 0f 85 30 01 00 00 f3 90 4c 89 ef be 08 00 00 00 e8 8f b0 61 00 <43> 80 3c 34 00 0f 84 64 fe ff ff 4c 89 ef e8 0c ae 61 00 e9 57 fe
RSP: 0018:ffffc9000e8e7720 EFLAGS: 00000256
RAX: 1ffff11023204001 RBX: ffff888118b41440 RCX: ffffffff815542d1
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffff888118bc9060
RBP: ffffc9000e8e7830 R08: ffff888118bc9067 R09: 1ffff1102317920c
R10: dffffc0000000000 R11: ffffed102317920d R12: 1ffff1102317920c
R13: ffff888118bc9060 R14: dffffc0000000000 R15: 1ffff92001d1cef4
mutex_optimistic_spin kernel/locking/mutex.c:494 [inline]
__mutex_lock_common kernel/locking/mutex.c:630 [inline]
__mutex_lock+0x338/0x1790 kernel/locking/mutex.c:775
__mutex_lock_interruptible_slowpath+0xe/0x10 kernel/locking/mutex.c:1076
mutex_lock_interruptible+0x10c/0x1b0 kernel/locking/mutex.c:1013
tty_write_lock+0x55/0x90 drivers/tty/tty_io.c:947
set_termios+0x483/0x6c0 drivers/tty/tty_ioctl.c:509
tty_mode_ioctl+0x4fc/0x680 drivers/tty/tty_ioctl.c:-1
n_tty_ioctl_helper+0x9f/0x310 drivers/tty/tty_ioctl.c:1001
n_tty_ioctl+0x13e/0x2c0 drivers/tty/n_tty.c:2510
tty_ioctl+0x8ef/0xc60 drivers/tty/tty_io.c:2785
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl+0x12f/0x1b0 fs/ioctl.c:856
__x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:856
x64_sys_call+0x58b/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:17
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: 0033:0x7f126d79e019
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:00007f126e641028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f126da26090 RCX: 00007f126d79e019
RDX: 00002000000000c0 RSI: 0000000000005403 RDI: 0000000000000004
RBP: 00007f126d83500c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f126da26128 R14: 00007f126da26090 R15: 00007fff00fbfe08
Allocated by task 496:
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 10:
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
exit_task_work include/linux/task_work.h:39 [inline]
do_exit+0xaf2/0x2850 kernel/exit.c:887
__do_sys_exit kernel/exit.c:996 [inline]
__se_sys_exit kernel/exit.c:994 [inline]
__cfi___ia32_sys_exit+0x0/0x10 kernel/exit.c:994
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 ffff888118cd7800
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
512-byte region [ffff888118cd7800, ffff888118cd7a00)
The buggy address belongs to the physical page:
page:ffffea0004633500 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x118cd4
head:ffffea0004633500 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 ffffea000469c300 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 113, tgid 113 (udevd), ts 8090991267, 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]
__alloc_skb+0x226/0x4a0 net/core/skbuff.c:518
alloc_skb include/linux/skbuff.h:1322 [inline]
alloc_skb_with_frags+0xa8/0x620 net/core/skbuff.c:6176
sock_alloc_send_pskb+0x87f/0x9a0 net/core/sock.c:2761
unix_dgram_sendmsg+0x5c1/0x1710 net/unix/af_unix.c:1947
sock_sendmsg_nosec net/socket.c:716 [inline]
__sock_sendmsg net/socket.c:728 [inline]
sock_write_iter+0x2ea/0x3f0 net/socket.c:1133
call_write_iter include/linux/fs.h:2282 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x5ef/0xd00 fs/read_write.c:584
page_owner free stack trace missing
Memory state around the buggy address:
ffff888118cd7880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888118cd7900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888118cd7980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888118cd7a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888118cd7a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
0: 3c 34 cmp $0x34,%al
2: 00 74 08 4c add %dh,0x4c(%rax,%rcx,1)
6: 89 ef mov %ebp,%edi
8: e8 3c ae 61 00 call 0x61ae49
d: 49 f7 45 00 01 00 00 testq $0x1,0x0(%r13)
14: 00
15: 0f 85 30 01 00 00 jne 0x14b
1b: f3 90 pause
1d: 4c 89 ef mov %r13,%rdi
20: be 08 00 00 00 mov $0x8,%esi
25: e8 8f b0 61 00 call 0x61b0b9
* 2a: 43 80 3c 34 00 cmpb $0x0,(%r12,%r14,1) <-- trapping instruction
2f: 0f 84 64 fe ff ff je 0xfffffe99
35: 4c 89 ef mov %r13,%rdi
38: e8 0c ae 61 00 call 0x61ae49
3d: e9 .byte 0xe9
3e: 57 push %rdi
3f: fe .byte 0xfe