==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff888112658190 by task syz.6.5180/17339

CPU: 1 PID: 17339 Comm: syz.6.5180 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
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:__sanitizer_cov_trace_cmp4+0x1/0x90 kernel/kcov.c:286
Code: 10 48 89 74 11 18 48 89 44 11 20 5d c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 90 90 90 90 90 90 90 90 90 90 90 b8 7d 47 2f 67 55 <48> 89 e5 48 8b 45 08 65 48 8b 15 e0 16 91 7e 65 8b 0d e1 16 91 7e
RSP: 0018:ffffc90000756de8 EFLAGS: 00000287
RAX: ffffffff81bc3b1c RBX: 0000000000000000 RCX: 0000000000080000
RDX: ffffc900026fe000 RSI: 0000000000000001 RDI: 0000000000000001
RBP: ffffc90000756e48 R08: ffff88810480e007 R09: 1ffff11020901c00
R10: dffffc0000000000 R11: ffffed1020901c01 R12: ffff88810480e040
R13: 000000000000000a R14: 0000000000000001 R15: 0000000000000001
 __set_page_owner+0x48/0x60 mm/page_owner.c:215
 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
 __folio_alloc+0x12/0x40 mm/page_alloc.c:5963
 __folio_alloc_node include/linux/gfp.h:245 [inline]
 folio_alloc include/linux/gfp.h:274 [inline]
 shmem_alloc_folio mm/shmem.c:1597 [inline]
 shmem_alloc_and_acct_folio+0x6dd/0x8c0 mm/shmem.c:1622
 shmem_get_folio_gfp+0xd6d/0x20f0 mm/shmem.c:1951
 shmem_fault+0x1ab/0x670 mm/shmem.c:2166
 __do_fault mm/memory.c:4376 [inline]
 do_read_fault mm/memory.c:4751 [inline]
 do_fault+0x19de/0x1e30 mm/memory.c:4887
 handle_pte_fault mm/memory.c:5183 [inline]
 __handle_mm_fault mm/memory.c:5325 [inline]
 handle_mm_fault+0x1363/0x26b0 mm/memory.c:5465
 faultin_page mm/gup.c:1026 [inline]
 __get_user_pages+0x34b/0xdb0 mm/gup.c:1250
 populate_vma_page_range mm/gup.c:1607 [inline]
 __mm_populate+0x2ea/0x430 mm/gup.c:1721
 mm_populate include/linux/mm.h:3148 [inline]
 vm_mmap_pgoff+0x271/0x3f0 mm/util.c:530
 ksys_mmap_pgoff+0xf6/0x1d0 mm/mmap.c:1537
 __do_sys_mmap arch/x86/kernel/sys_x86_64.c:93 [inline]
 __se_sys_mmap arch/x86/kernel/sys_x86_64.c:86 [inline]
 __x64_sys_mmap+0xfa/0x110 arch/x86/kernel/sys_x86_64.c:86
 x64_sys_call+0x8fd/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:10
 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: 0033:0x7faed799ce59
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:00007faed8770028 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007faed7c15fa0 RCX: 00007faed799ce59
RDX: b635773f06ebbeee RSI: 0000000000b36000 RDI: 0000200000000000
RBP: 00007faed7a32e6f R08: ffffffffffffffff R09: 0000000000000000
R10: 0000000000008031 R11: 0000000000000246 R12: 0000000000000000
R13: 00007faed7c16038 R14: 00007faed7c15fa0 R15: 00007ffe05779f58
 </TASK>

Allocated by task 17302:
 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 17303:
 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
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0x9b/0xb0 kernel/entry/common.c:177
 exit_to_user_mode_prepare+0x87/0xd0 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
 syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:303
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff888112658000
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
 512-byte region [ffff888112658000, ffff888112658200)

The buggy address belongs to the physical page:
page:ffffea0004499600 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x112658
head:ffffea0004499600 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 ffffea0004354000 dead000000000002 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 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 16665, tgid 16664 (syz.6.4966), ts 780816666527, free_ts 775409869753
 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
 kmalloc_trace+0x29/0xb0 mm/slab_common.c:1028
 kmalloc include/linux/slab.h:563 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 assoc_array_insert+0x8f/0x3340 lib/assoc_array.c:980
 __key_link_begin+0xe1/0x210 security/keys/keyring.c:1317
 key_create_or_update+0x4e2/0x9f0 security/keys/key.c:882
 __do_sys_add_key security/keys/keyctl.c:134 [inline]
 __se_sys_add_key+0x34b/0x410 security/keys/keyctl.c:74
 __x64_sys_add_key+0xbf/0xd0 security/keys/keyctl.c:74
 x64_sys_call+0x6aa/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:249
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1580 [inline]
 free_pcp_prepare mm/page_alloc.c:1654 [inline]
 free_unref_page_prepare+0x80c/0x820 mm/page_alloc.c:3621
 free_unref_page+0x93/0x530 mm/page_alloc.c:3719
 free_the_page mm/page_alloc.c:863 [inline]
 __free_pages+0x67/0x100 mm/page_alloc.c:6020
 __vunmap+0xa3c/0xc00 mm/vmalloc.c:2739
 __vfree mm/vmalloc.c:2788 [inline]
 vfree+0x61/0x90 mm/vmalloc.c:2819
 kcov_put kernel/kcov.c:437 [inline]
 kcov_close+0x2b/0x50 kernel/kcov.c:533
 __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+0xa7c/0x27c0 kernel/exit.c:886
 do_group_exit+0x21b/0x2e0 kernel/exit.c:1029
 __do_sys_exit_group kernel/exit.c:1040 [inline]
 __se_sys_exit_group kernel/exit.c:1038 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1038
 x64_sys_call+0x7b4/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:232
 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

Memory state around the buggy address:
 ffff888112658080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888112658100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888112658180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff888112658200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888112658280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
   0:	10 48 89             	adc    %cl,-0x77(%rax)
   3:	74 11                	je     0x16
   5:	18 48 89             	sbb    %cl,-0x77(%rax)
   8:	44 11 20             	adc    %r12d,(%rax)
   b:	5d                   	pop    %rbp
   c:	c3                   	ret
   d:	66 2e 0f 1f 84 00 00 	cs nopw 0x0(%rax,%rax,1)
  14:	00 00 00
  17:	66 90                	xchg   %ax,%ax
  19:	90                   	nop
  1a:	90                   	nop
  1b:	90                   	nop
  1c:	90                   	nop
  1d:	90                   	nop
  1e:	90                   	nop
  1f:	90                   	nop
  20:	90                   	nop
  21:	90                   	nop
  22:	90                   	nop
  23:	90                   	nop
  24:	b8 7d 47 2f 67       	mov    $0x672f477d,%eax
  29:	55                   	push   %rbp
* 2a:	48 89 e5             	mov    %rsp,%rbp <-- trapping instruction
  2d:	48 8b 45 08          	mov    0x8(%rbp),%rax
  31:	65 48 8b 15 e0 16 91 	mov    %gs:0x7e9116e0(%rip),%rdx        # 0x7e911719
  38:	7e
  39:	65 8b 0d e1 16 91 7e 	mov    %gs:0x7e9116e1(%rip),%ecx        # 0x7e911721