================================================================== BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75 Read of size 8 at addr ffff88813374b590 by task syz.0.141/861 CPU: 1 PID: 861 Comm: syz.0.141 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026 Call Trace: __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+0x1dd/0x5f0 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 asm_sysvec_apic_timer_interrupt+0x1b/0x20 arch/x86/include/asm/idtentry.h:691 RIP: 0010:finish_task_switch+0x173/0x7c0 kernel/sched/core.c:5302 Code: 80 3c 2b 00 74 08 4c 89 f7 e8 49 a7 69 00 4d 8b 2e 4d 85 ed 0f 85 cd 00 00 00 4c 89 e7 e8 25 ab b4 03 fb 49 8d 9f 48 0b 00 00 <48> 89 d8 48 c1 e8 03 49 bd 00 00 00 00 00 fc ff df 42 0f b6 04 28 RSP: 0018:ffffc9000a3e7348 EFLAGS: 00000282 RAX: 0000000080000001 RBX: ffff888113fb0b48 RCX: 0000000000000000 RDX: 0000000000000001 RSI: ffffffff85ca7540 RDI: 00000000ffffffff RBP: ffffc9000a3e7390 R08: ffff888116f98007 R09: 1ffff11022df3000 R10: dffffc0000000000 R11: ffffed1022df3001 R12: ffff8881f6f37f00 R13: 0000000000000000 R14: ffff8881f6f38a60 R15: ffff888113fb0000 context_switch kernel/sched/core.c:5428 [inline] __schedule+0xcbb/0x1700 kernel/sched/core.c:6762 preempt_schedule_common+0x9b/0xf0 kernel/sched/core.c:6931 preempt_schedule+0xbc/0xd0 kernel/sched/core.c:6955 preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:34 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline] _raw_spin_unlock_irqrestore+0x6f/0x80 kernel/locking/spinlock.c:194 spin_unlock_irqrestore include/linux/spinlock.h:406 [inline] __wake_up_common_lock kernel/sched/wait.c:141 [inline] __wake_up_sync_key+0x17b/0x2b0 kernel/sched/wait.c:212 __unix_dgram_recvmsg+0x4b5/0xd90 net/unix/af_unix.c:2492 unix_dgram_recvmsg+0xc7/0xe0 net/unix/af_unix.c:2562 ____sys_recvmsg+0x2d6/0x5c0 net/socket.c:-1 ___sys_recvmsg+0x210/0x590 net/socket.c:2770 do_recvmmsg+0x370/0x7e0 net/socket.c:2864 __sys_recvmmsg net/socket.c:2943 [inline] __do_sys_recvmmsg net/socket.c:2966 [inline] __se_sys_recvmmsg net/socket.c:2959 [inline] __x64_sys_recvmmsg+0x195/0x250 net/socket.c:2959 x64_sys_call+0x3e7/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:300 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: 0033:0x7f52eb39fb19 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:00007f52ec253028 EFLAGS: 00000246 ORIG_RAX: 000000000000012b RAX: ffffffffffffffda RBX: 00007f52eb626090 RCX: 00007f52eb39fb19 RDX: 0000000000010106 RSI: 00002000000000c0 RDI: 0000000000000006 RBP: 00007f52eb437b70 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f52eb626128 R14: 00007f52eb626090 R15: 00007fff14e21358 Allocated by task 869: 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 10: 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 ffff88813374b400 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 400 bytes inside of 512-byte region [ffff88813374b400, ffff88813374b600) The buggy address belongs to the physical page: page:ffffea0004cdd200 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x133748 head:ffffea0004cdd200 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x4000000000010200(slab|head|zone=1) raw: 4000000000010200 ffffea0004cdf000 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 287, tgid 287 (syz-executor), ts 26452617404, 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] netlink_alloc_large_skb net/netlink/af_netlink.c:1183 [inline] netlink_sendmsg+0x635/0xbd0 net/netlink/af_netlink.c:1853 sock_sendmsg_nosec net/socket.c:716 [inline] __sock_sendmsg net/socket.c:728 [inline] __sys_sendto+0x4ac/0x660 net/socket.c:2143 __do_sys_sendto net/socket.c:2155 [inline] __se_sys_sendto net/socket.c:2151 [inline] __x64_sys_sendto+0xe5/0x100 net/socket.c:2151 x64_sys_call+0x83/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:45 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76 page_owner free stack trace missing Memory state around the buggy address: ffff88813374b480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88813374b500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88813374b580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88813374b600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88813374b680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ================================================================== ---------------- Code disassembly (best guess): 0: 80 3c 2b 00 cmpb $0x0,(%rbx,%rbp,1) 4: 74 08 je 0xe 6: 4c 89 f7 mov %r14,%rdi 9: e8 49 a7 69 00 call 0x69a757 e: 4d 8b 2e mov (%r14),%r13 11: 4d 85 ed test %r13,%r13 14: 0f 85 cd 00 00 00 jne 0xe7 1a: 4c 89 e7 mov %r12,%rdi 1d: e8 25 ab b4 03 call 0x3b4ab47 22: fb sti 23: 49 8d 9f 48 0b 00 00 lea 0xb48(%r15),%rbx * 2a: 48 89 d8 mov %rbx,%rax <-- trapping instruction 2d: 48 c1 e8 03 shr $0x3,%rax 31: 49 bd 00 00 00 00 00 movabs $0xdffffc0000000000,%r13 38: fc ff df 3b: 42 0f b6 04 28 movzbl (%rax,%r13,1),%eax