==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff8881127e9990 by task udevd/102

CPU: 1 PID: 102 Comm: udevd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <IRQ>
 __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
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1b/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:handle_mounts fs/namei.c:1540 [inline]
RIP: 0010:step_into+0x1f7/0xf00 fs/namei.c:1843
Code: 04 08 84 c0 0f 85 ed 0b 00 00 41 80 0f 04 49 bf 00 00 00 00 00 fc ff df eb 6f 48 8d 53 44 48 89 d0 48 c1 e8 03 48 89 44 24 28 <42> 0f b6 04 38 84 c0 0f 85 24 0b 00 00 8b 02 89 44 24 3c 4c 89 e8
RSP: 0018:ffffc90000a076c0 EFLAGS: 00000a03
RAX: 1ffff92000140f40 RBX: ffffc90000a079c0 RCX: 0000000000000000
RDX: ffffc90000a07a04 RSI: 0000000000000040 RDI: 0000000000000000
RBP: ffffc90000a077b0 R08: ffff88810b6cecf8 R09: 1ffff110216d9d9f
R10: dffffc0000000000 R11: ffffed10216d9da0 R12: 1ffff92000140f3f
R13: ffff88810b6cecc0 R14: 0000000000000051 R15: dffffc0000000000
 walk_component fs/namei.c:2011 [inline]
 link_path_walk+0x744/0xeb0 fs/namei.c:2332
 path_lookupat+0x8d/0x430 fs/namei.c:2485
 filename_lookup+0x229/0x580 fs/namei.c:2515
 vfs_statx+0x11b/0x6b0 fs/stat.c:229
 vfs_fstatat fs/stat.c:267 [inline]
 __do_sys_newfstatat fs/stat.c:437 [inline]
 __se_sys_newfstatat+0x142/0x440 fs/stat.c:431
 __x64_sys_newfstatat+0x9b/0xb0 fs/stat.c:431
 x64_sys_call+0x77c/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:263
 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: 0033:0x7f258f511b0a
Code: 48 8b 15 f1 f2 0d 00 f7 d8 64 89 02 b8 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 41 89 ca b8 06 01 00 00 0f 05 <3d> 00 f0 ff ff 77 07 31 c0 c3 0f 1f 40 00 48 8b 15 b9 f2 0d 00 f7
RSP: 002b:00007ffc6bb90e48 EFLAGS: 00000246 ORIG_RAX: 0000000000000106
RAX: ffffffffffffffda RBX: 00007ffc6bb912e0 RCX: 00007f258f511b0a
RDX: 00007ffc6bb90e50 RSI: 00007ffc6bb912e0 RDI: 00000000ffffff9c
RBP: 00005583381ad2c0 R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffc6bb90ee0
R13: 0000000000000100 R14: 0000558308c40be0 R15: 00007ffc6bb91960
 </TASK>

Allocated by task 377:
 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:1614
 pppol2tp_connect+0xbf5/0x1640 net/l2tp/l2tp_ppp.c:771
 __sys_connect_file net/socket.c:2001 [inline]
 __sys_connect+0x3da/0x460 net/socket.c:2018
 __do_sys_connect net/socket.c:2028 [inline]
 __se_sys_connect net/socket.c:2025 [inline]
 __x64_sys_connect+0x7a/0x90 net/socket.c:2025
 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 8:
 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:1587
 l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1233 [inline]
 l2tp_tunnel_del_work+0x199/0x410 net/l2tp/l2tp_core.c:1271
 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:1390
 __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+0xb0d/0x29f0 kernel/exit.c:896
 __do_sys_exit kernel/exit.c:1006 [inline]
 __se_sys_exit kernel/exit.c:1004 [inline]
 __cfi___ia32_sys_exit+0x0/0x10 kernel/exit.c:1004
 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 ffff8881127e9800
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
 512-byte region [ffff8881127e9800, ffff8881127e9a00)

The buggy address belongs to the physical page:
page:ffffea000449fa00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1127e8
head:ffffea000449fa00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 dead000000000100 dead000000000122 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 103, tgid 103 (udevadm), ts 6869142448, free_ts 0
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2673
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2680
 get_page_from_freelist+0x2ca9/0x2d20 mm/page_alloc.c:4587
 __alloc_pages+0x1fa/0x610 mm/page_alloc.c:5931
 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_uevent_skb+0x85/0x240 lib/kobject_uevent.c:290
 uevent_net_broadcast_untagged lib/kobject_uevent.c:326 [inline]
 kobject_uevent_net_broadcast+0x343/0x5b0 lib/kobject_uevent.c:409
 kobject_uevent_env+0x541/0x720 lib/kobject_uevent.c:608
 kobject_synth_uevent+0x457/0x940 lib/kobject_uevent.c:208
 store_uevent+0x16/0x30 kernel/module/main.c:927
page_owner free stack trace missing

Memory state around the buggy address:
 ffff8881127e9880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881127e9900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881127e9980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff8881127e9a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8881127e9a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
   0:	04 08                	add    $0x8,%al
   2:	84 c0                	test   %al,%al
   4:	0f 85 ed 0b 00 00    	jne    0xbf7
   a:	41 80 0f 04          	orb    $0x4,(%r15)
   e:	49 bf 00 00 00 00 00 	movabs $0xdffffc0000000000,%r15
  15:	fc ff df
  18:	eb 6f                	jmp    0x89
  1a:	48 8d 53 44          	lea    0x44(%rbx),%rdx
  1e:	48 89 d0             	mov    %rdx,%rax
  21:	48 c1 e8 03          	shr    $0x3,%rax
  25:	48 89 44 24 28       	mov    %rax,0x28(%rsp)
* 2a:	42 0f b6 04 38       	movzbl (%rax,%r15,1),%eax <-- trapping instruction
  2f:	84 c0                	test   %al,%al
  31:	0f 85 24 0b 00 00    	jne    0xb5b
  37:	8b 02                	mov    (%rdx),%eax
  39:	89 44 24 3c          	mov    %eax,0x3c(%rsp)
  3d:	4c 89 e8             	mov    %r13,%rax