==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff88810f593590 by task syz-execprog/288

CPU: 0 PID: 288 Comm: syz-execprog Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
Call Trace:
 <IRQ>
 __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
 </IRQ>
 __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:__kasan_check_read+0x0/0x20 mm/kasan/shadow.c:30
Code: 5b 41 5c 41 5d 41 5e 41 5f 5d c3 48 c7 c7 01 a6 bd 85 eb 0a 48 c7 c7 86 44 b3 85 48 89 de e8 37 0b db 02 45 31 ff eb d1 00 00 <55> 48 89 e5 89 f6 48 8b 4d 08 31 d2 e8 af ed ff ff 5d c3 66 2e 0f
RSP: 0018:ffffc9000096f5b8 EFLAGS: 00000286
RAX: 8000000116d53005 RBX: 8000000116d53025 RCX: ffff8881081dd000
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffff8881081dd000
RBP: ffffc9000096f7b0 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff0dd66fc R12: 1ffff9200012dee0
R13: dffffc0000000000 R14: 1ffff11020c7bbaf R15: ffff8881081dd000
 unmap_single_vma mm/memory.c:1551 [inline]
 unmap_vmas+0x25f/0x360 mm/memory.c:1583
 exit_mmap+0x309/0x590 mm/mmap.c:3385
 __mmput+0x92/0x2d0 kernel/fork.c:1153
 mmput+0x4e/0x150 kernel/fork.c:1176
 exit_mm kernel/exit.c:546 [inline]
 do_exit+0x9d8/0x24e0 kernel/exit.c:866
 do_group_exit+0x149/0x310 kernel/exit.c:993
 get_signal+0xfb1/0x1300 kernel/signal.c:2806
 arch_do_signal_or_restart+0xe7/0x11b0 arch/x86/kernel/signal.c:805
 handle_signal_work kernel/entry/common.c:148 [inline]
 exit_to_user_mode_loop+0xa2/0xe0 kernel/entry/common.c:172
 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
RIP: 0033:0x48ecf7
Code: Unable to access opcode bytes at RIP 0x48eccd.
RSP: 002b:00001d61e9e7df00 EFLAGS: 00000202 ORIG_RAX: 0000000000000023
RAX: 0000000000000000 RBX: 0000000000000014 RCX: 000000000048ecf7
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00001d61e9e7df00
RBP: 00001d61e9e7df10 R08: 000000000000001b R09: 0008eff656f653e0
R10: 0000000fae502ad8 R11: 0000000000000202 R12: 00001d61e9e7df00
R13: 00001d61e9e92001 R14: 00001d61e9e525a0 R15: ffffffffffffffff

Allocated by task 388:
 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 317:
 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 ffff88810f593400
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
 512-byte region [ffff88810f593400, ffff88810f593600)
The buggy address belongs to the page:
page:ffffea00043d6400 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10f590
head:ffffea00043d6400 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 ffffea00043ffc00 0000000700000007 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 103, ts 3857222985, 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:6058
 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:
 ffff88810f593480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88810f593500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88810f593580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff88810f593600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88810f593680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
   0:	5b                   	pop    %rbx
   1:	41 5c                	pop    %r12
   3:	41 5d                	pop    %r13
   5:	41 5e                	pop    %r14
   7:	41 5f                	pop    %r15
   9:	5d                   	pop    %rbp
   a:	c3                   	ret
   b:	48 c7 c7 01 a6 bd 85 	mov    $0xffffffff85bda601,%rdi
  12:	eb 0a                	jmp    0x1e
  14:	48 c7 c7 86 44 b3 85 	mov    $0xffffffff85b34486,%rdi
  1b:	48 89 de             	mov    %rbx,%rsi
  1e:	e8 37 0b db 02       	call   0x2db0b5a
  23:	45 31 ff             	xor    %r15d,%r15d
  26:	eb d1                	jmp    0xfffffff9
  28:	00 00                	add    %al,(%rax)
* 2a:	55                   	push   %rbp <-- trapping instruction
  2b:	48 89 e5             	mov    %rsp,%rbp
  2e:	89 f6                	mov    %esi,%esi
  30:	48 8b 4d 08          	mov    0x8(%rbp),%rcx
  34:	31 d2                	xor    %edx,%edx
  36:	e8 af ed ff ff       	call   0xffffedea
  3b:	5d                   	pop    %rbp
  3c:	c3                   	ret
  3d:	66                   	data16
  3e:	2e                   	cs
  3f:	0f                   	.byte 0xf