==================================================================
BUG: KASAN: use-after-free in rcu_segcblist_restempty kernel/rcu/rcu_segcblist.h:110 [inline]
BUG: KASAN: use-after-free in rcu_segcblist_accelerate+0x1e7/0x420 kernel/rcu/rcu_segcblist.c:581
Read of size 8 at addr ffff88810f83ad90 by task syz.7.274/1413

CPU: 1 PID: 1413 Comm: syz.7.274 Tainted: G        W         syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <IRQ>
 __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_segcblist_restempty kernel/rcu/rcu_segcblist.h:110 [inline]
 rcu_segcblist_accelerate+0x1e7/0x420 kernel/rcu/rcu_segcblist.c:581
 rcu_accelerate_cbs kernel/rcu/tree.c:1521 [inline]
 rcu_report_qs_rdp kernel/rcu/tree.c:2326 [inline]
 rcu_check_quiescent_state kernel/rcu/tree.c:2366 [inline]
 rcu_core+0x7d2/0xef0 kernel/rcu/tree.c:2747
 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
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1b/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:unwind_get_return_address+0x56/0x90 arch/x86/kernel/unwind_frame.c:19
Code: 83 c3 48 49 89 df 49 c1 ef 03 43 80 3c 37 00 74 08 48 89 df e8 9b 6d 77 00 48 8b 3b e8 f3 84 13 00 85 c0 74 14 43 80 3c 37 00 <74> 08 48 89 df e8 80 6d 77 00 48 8b 03 eb 02 31 c0 5b 41 5e 41 5f
RSP: 0000:ffffc900012371e0 EFLAGS: 00000246
RAX: 0000000000000001 RBX: ffffc90001237250 RCX: 0000000000246e01
RDX: ffffc90001237cb0 RSI: 1ffff92000246e42 RDI: ffffffff81320ec8
RBP: ffffc900012371f8 R08: ffffc900012372d0 R09: ffffc900012372c8
R10: 0000000000000006 R11: fffff52000246e4d R12: ffff8881106e2780
R13: 1ffff110220dc5a2 R14: dffffc0000000000 R15: 1ffff92000246e4a
 arch_stack_walk+0xee/0x140 arch/x86/kernel/stacktrace.c:26
 stack_trace_save+0xa6/0xf0 kernel/stacktrace.c:122
 save_stack+0x121/0x230 mm/page_owner.c:139
 __set_page_owner+0x2b/0x2e0 mm/page_owner.c:200
 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_pages_node include/linux/gfp.h:595 [inline]
 alloc_pages_node include/linux/gfp.h:609 [inline]
 alloc_pages include/linux/gfp.h:622 [inline]
 __pte_alloc_one include/asm-generic/pgalloc.h:63 [inline]
 pte_alloc_one+0x70/0x190 arch/x86/mm/pgtable.c:33
 do_fault_around mm/memory.c:4519 [inline]
 do_read_fault mm/memory.c:4561 [inline]
 do_fault mm/memory.c:4709 [inline]
 handle_pte_fault+0x19d0/0x2770 mm/memory.c:4923
 __handle_mm_fault mm/memory.c:-1 [inline]
 do_handle_mm_fault+0x1b3b/0x1e30 mm/memory.c:5345
 handle_mm_fault include/linux/mm.h:1847 [inline]
 do_user_addr_fault+0x808/0x11c0 arch/x86/mm/fault.c:1416
 handle_page_fault arch/x86/mm/fault.c:1507 [inline]
 exc_page_fault+0x51/0xb0 arch/x86/mm/fault.c:1560
 asm_exc_page_fault+0x27/0x30 arch/x86/include/asm/idtentry.h:606
RIP: 0033:0x7f8231d03615
Code: ff 0f 1f 40 00 53 48 8b 1d a8 27 3c 00 45 31 d2 31 c9 48 8b 17 45 31 db 4c 8d 83 00 00 40 00 48 89 d0 0f 1f 00 4c 39 c0 73 63 <44> 0f b6 08 48 83 c0 01 4c 89 ce 83 e6 7f 48 d3 e6 49 09 f2 45 84
RSP: 002b:00007ffce7c0e080 EFLAGS: 00010287
RAX: 0000001b33b20000 RBX: 0000001b33b20000 RCX: 0000000000000000
RDX: 0000001b33b20000 RSI: 00007ffce7c0e070 RDI: 00007ffce7c0e170
RBP: 00000000000167ff R08: 0000001b33f20000 R09: 00088c65d8ba4030
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 00000000000167ff R15: 00007ffce7c0e320
 </TASK>

Allocated by task 1412:
 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:1922 [inline]
 __sys_connect+0x3cb/0x450 net/socket.c:1939
 __do_sys_connect net/socket.c:1949 [inline]
 __se_sys_connect net/socket.c:1946 [inline]
 __x64_sys_connect+0x7a/0x90 net/socket.c:1946
 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 370:
 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:1335
 __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 ffff88810f83ac00
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
 512-byte region [ffff88810f83ac00, ffff88810f83ae00)
The buggy address belongs to the page:
page:ffffea00043e0e00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10f838
head:ffffea00043e0e00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 ffffea00043fb500 0000000200000002 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 4065377159, 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
 uevent_store+0x4b/0x70 drivers/base/bus.c:583
 drv_attr_store+0x79/0xa0 drivers/base/bus.c:77
 sysfs_kf_write+0x129/0x150 fs/sysfs/file.c:139
page_owner free stack trace missing

Memory state around the buggy address:
 ffff88810f83ac80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88810f83ad00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88810f83ad80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff88810f83ae00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88810f83ae80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
   0:	83 c3 48             	add    $0x48,%ebx
   3:	49 89 df             	mov    %rbx,%r15
   6:	49 c1 ef 03          	shr    $0x3,%r15
   a:	43 80 3c 37 00       	cmpb   $0x0,(%r15,%r14,1)
   f:	74 08                	je     0x19
  11:	48 89 df             	mov    %rbx,%rdi
  14:	e8 9b 6d 77 00       	call   0x776db4
  19:	48 8b 3b             	mov    (%rbx),%rdi
  1c:	e8 f3 84 13 00       	call   0x138514
  21:	85 c0                	test   %eax,%eax
  23:	74 14                	je     0x39
  25:	43 80 3c 37 00       	cmpb   $0x0,(%r15,%r14,1)
* 2a:	74 08                	je     0x34 <-- trapping instruction
  2c:	48 89 df             	mov    %rbx,%rdi
  2f:	e8 80 6d 77 00       	call   0x776db4
  34:	48 8b 03             	mov    (%rbx),%rax
  37:	eb 02                	jmp    0x3b
  39:	31 c0                	xor    %eax,%eax
  3b:	5b                   	pop    %rbx
  3c:	41 5e                	pop    %r14
  3e:	41 5f                	pop    %r15