==================================================================
BUG: KASAN: use-after-free in rcu_segcblist_restempty kernel/rcu/rcu_segcblist.h:75 [inline]
BUG: KASAN: use-after-free in rcu_segcblist_accelerate+0x1e1/0x320 kernel/rcu/rcu_segcblist.c:487
Read of size 8 at addr ffff888111849d90 by task syz.0.1468/6005

CPU: 1 PID: 6005 Comm: syz.0.1468 Tainted: G        W         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: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_segcblist_restempty kernel/rcu/rcu_segcblist.h:75 [inline]
 rcu_segcblist_accelerate+0x1e1/0x320 kernel/rcu/rcu_segcblist.c:487
 rcu_accelerate_cbs+0x59/0x430 kernel/rcu/tree.c:1510
 rcu_advance_cbs kernel/rcu/tree.c:1575 [inline]
 __note_gp_changes+0x1c5/0x760 kernel/rcu/tree.c:1629
 note_gp_changes+0x131/0x230 kernel/rcu/tree.c:1675
 rcu_check_quiescent_state kernel/rcu/tree.c:2319 [inline]
 rcu_core+0x249/0xca0 kernel/rcu/tree.c:2719
 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:memset_erms+0xb/0x10 arch/x86/lib/memset_64.S:65
Code: 03 40 0f b6 f6 48 b8 01 01 01 01 01 01 01 01 48 0f af c6 f3 48 ab 89 d1 f3 aa 4c 89 c8 c3 90 49 89 f9 40 88 f0 48 89 d1 f3 aa <4c> 89 c8 c3 90 49 89 fa 40 0f b6 ce 48 b8 01 01 01 01 01 01 01 01
RSP: 0018:ffffc90002307470 EFLAGS: 00000202
RAX: ffffc90002307500 RBX: 0000000000000038 RCX: 0000000000000000
RDX: 0000000000000038 RSI: 0000000000000000 RDI: ffffc90002307538
RBP: ffffc90002307490 R08: ffffc90002307537 R09: ffffc90002307500
R10: dffffc0000000000 R11: fffff52000460ea7 R12: 1ffff92000460e9c
R13: ffffc90002307560 R14: 0000000000000000 R15: ffffc90002307500
 avc_has_perm_noaudit security/selinux/avc.c:1152 [inline]
 avc_has_perm+0xec/0x3d0 security/selinux/avc.c:1198
 selinux_socket_unix_may_send+0x1e6/0x2c0 security/selinux/hooks.c:5043
 security_unix_may_send+0x6b/0xa0 security/security.c:2115
 unix_dgram_sendmsg+0xd76/0x18f0 net/unix/af_unix.c:1805
 sock_sendmsg_nosec net/socket.c:652 [inline]
 __sock_sendmsg net/socket.c:664 [inline]
 ____sys_sendmsg+0x5be/0x8f0 net/socket.c:2377
 ___sys_sendmsg+0x236/0x2e0 net/socket.c:2431
 __sys_sendmmsg+0x2ab/0x4c0 net/socket.c:2517
 __do_sys_sendmmsg net/socket.c:2546 [inline]
 __se_sys_sendmmsg net/socket.c:2543 [inline]
 __x64_sys_sendmmsg+0xa0/0xb0 net/socket.c:2543
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7faf9051d159
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:00007faf8ef76028 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007faf907a4fa0 RCX: 00007faf9051d159
RDX: 0000000000000651 RSI: 0000200000000000 RDI: 0000000000000006
RBP: 00007faf905b4024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007faf907a5038 R14: 00007faf907a4fa0 R15: 00007ffe94095af8

Allocated by task 6000:
 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 416:
 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:172
 exit_to_user_mode_prepare+0x76/0xa0 kernel/entry/common.c:199
 syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:274
 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 ffff888111849c00
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
 512-byte region [ffff888111849c00, ffff888111849e00)
The buggy address belongs to the page:
page:ffffea0004461200 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x111848
head:ffffea0004461200 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 dead000000000100 dead000000000122 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 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 6000, ts 224821908269, free_ts 224779665493
 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+0x1f9/0x330 mm/slub.c:4034
 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
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:28 [inline]
 free_pages_prepare mm/page_alloc.c:1349 [inline]
 __free_pages_ok+0x80b/0x830 mm/page_alloc.c:1629
 free_the_page mm/page_alloc.c:5445 [inline]
 __free_pages+0xd8/0x390 mm/page_alloc.c:5454
 __free_slab+0xcf/0x190 mm/slub.c:1899
 free_slab mm/slub.c:1914 [inline]
 discard_slab+0x29/0x40 mm/slub.c:1920
 __slab_free+0x313/0x3a0 mm/slub.c:3136
 do_slab_free mm/slub.c:3196 [inline]
 ___cache_free+0x10e/0x130 mm/slub.c:3215
 qlink_free+0x50/0x90 mm/kasan/quarantine.c:157
 qlist_free_all+0x5f/0xb0 mm/kasan/quarantine.c:176
 kasan_quarantine_reduce+0x14a/0x160 mm/kasan/quarantine.c:283
 __kasan_slab_alloc+0x2f/0xe0 mm/kasan/common.c:440
 kasan_slab_alloc include/linux/kasan.h:244 [inline]
 slab_post_alloc_hook+0x5d/0x2f0 mm/slab.h:580
 slab_alloc_node mm/slub.c:2952 [inline]
 slab_alloc mm/slub.c:2960 [inline]
 kmem_cache_alloc+0x15a/0x2d0 mm/slub.c:2965
 vm_area_alloc+0x24/0x160 kernel/fork.c:358
 __mmap_region mm/mmap.c:1859 [inline]
 mmap_region+0xa5e/0x19c0 mm/mmap.c:3075
 do_mmap+0x85f/0xf50 mm/mmap.c:1661
 vm_mmap_pgoff+0x1f4/0x350 mm/util.c:543

Memory state around the buggy address:
 ffff888111849c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888111849d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888111849d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff888111849e00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888111849e80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
   0:	03 40 0f             	add    0xf(%rax),%eax
   3:	b6 f6                	mov    $0xf6,%dh
   5:	48 b8 01 01 01 01 01 	movabs $0x101010101010101,%rax
   c:	01 01 01
   f:	48 0f af c6          	imul   %rsi,%rax
  13:	f3 48 ab             	rep stos %rax,%es:(%rdi)
  16:	89 d1                	mov    %edx,%ecx
  18:	f3 aa                	rep stos %al,%es:(%rdi)
  1a:	4c 89 c8             	mov    %r9,%rax
  1d:	c3                   	ret
  1e:	90                   	nop
  1f:	49 89 f9             	mov    %rdi,%r9
  22:	40 88 f0             	mov    %sil,%al
  25:	48 89 d1             	mov    %rdx,%rcx
  28:	f3 aa                	rep stos %al,%es:(%rdi)
* 2a:	4c 89 c8             	mov    %r9,%rax <-- trapping instruction
  2d:	c3                   	ret
  2e:	90                   	nop
  2f:	49 89 fa             	mov    %rdi,%r10
  32:	40 0f b6 ce          	movzbl %sil,%ecx
  36:	48 b8 01 01 01 01 01 	movabs $0x101010101010101,%rax
  3d:	01 01 01