================================================================== BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75 Read of size 8 at addr ffff88811953c590 by task syz.4.112/1073 CPU: 1 PID: 1073 Comm: syz.4.112 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026 Call Trace: __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 __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:native_save_fl arch/x86/include/asm/irqflags.h:22 [inline] RIP: 0010:arch_local_save_flags arch/x86/include/asm/irqflags.h:79 [inline] RIP: 0010:arch_local_irq_save arch/x86/include/asm/irqflags.h:120 [inline] RIP: 0010:console_unlock+0xc2c/0x10d0 kernel/printk/printk.c:2497 Code: 00 48 c7 c7 c0 4d ea 86 e8 71 1f 35 03 80 fb 01 48 8b 5c 24 20 0f 84 7f 04 00 00 e8 be 59 00 00 48 89 5c 24 70 ff 74 24 70 9d <41> c6 45 22 00 48 c7 84 24 90 01 00 00 00 00 00 00 9c 8f 84 24 90 RSP: 0018:ffffc900014669c0 EFLAGS: 00000283 RAX: ffffffff814d8ec9 RBX: 0000000000000283 RCX: 0000000000080000 RDX: ffffc90003d14000 RSI: 00000000000013a3 RDI: 00000000000013a4 RBP: ffffc90001466c90 R08: 0000000000000003 R09: 0000000000000004 R10: dffffc0000000000 R11: fffff5200028cd28 R12: dffffc0000000000 R13: fffff5200028cd48 R14: 0000000000000000 R15: 0000000000000000 vprintk_emit+0x1a3/0x340 kernel/printk/printk.c:2069 vprintk_default+0x26/0x30 kernel/printk/printk.c:2086 vprintk_func+0x1a3/0x1e0 kernel/printk/printk_safe.c:401 printk+0xda/0x130 kernel/printk/printk.c:2117 __nla_validate_parse+0x1f13/0x2780 lib/nlattr.c:603 __nla_parse+0x42/0x60 lib/nlattr.c:688 __nlmsg_parse include/net/netlink.h:733 [inline] nlmsg_parse_deprecated include/net/netlink.h:772 [inline] rtnl_dellink+0x203/0x770 net/core/rtnetlink.c:3110 rtnetlink_rcv_msg+0x9e9/0xca0 net/core/rtnetlink.c:5622 netlink_rcv_skb+0x1e9/0x430 net/netlink/af_netlink.c:2508 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:5640 netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline] netlink_unicast+0x86c/0xa30 net/netlink/af_netlink.c:1340 netlink_sendmsg+0x949/0xb70 net/netlink/af_netlink.c:1919 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_sendmsg net/socket.c:2460 [inline] __do_sys_sendmsg net/socket.c:2469 [inline] __se_sys_sendmsg net/socket.c:2467 [inline] __x64_sys_sendmsg+0x201/0x2d0 net/socket.c:2467 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x61/0xcb RIP: 0033:0x7fb81f34b159 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:00007fb81dd83028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007fb81f5d3090 RCX: 00007fb81f34b159 RDX: 0000000000000000 RSI: 0000200000000200 RDI: 0000000000000005 RBP: 00007fb81f3e206b R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fb81f5d3128 R14: 00007fb81f5d3090 R15: 00007ffe67917d48 Allocated by task 1062: 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 112: 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 exit_task_work include/linux/task_work.h:33 [inline] do_exit+0xa7c/0x24e0 kernel/exit.c:879 do_group_exit+0x149/0x310 kernel/exit.c:993 get_signal+0xfb1/0x1300 kernel/signal.c:2802 arch_do_signal_or_restart+0xe7/0x11b0 arch/x86/kernel/signal.c:805 handle_signal_work kernel/entry/common.c:145 [inline] exit_to_user_mode_loop+0xa2/0xe0 kernel/entry/common.c:169 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 ffff88811953c400 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 400 bytes inside of 512-byte region [ffff88811953c400, ffff88811953c600) The buggy address belongs to the page: page:ffffea0004654f00 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88811953d000 pfn:0x11953c head:ffffea0004654f00 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x4000000000010200(slab|head) raw: 4000000000010200 ffffea00045f6e00 0000000500000005 ffff888100043080 raw: ffff88811953d000 000000008010000f 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 107, ts 4775043723, 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:6045 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: ffff88811953c480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88811953c500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88811953c580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88811953c600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88811953c680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ================================================================== ---------------- Code disassembly (best guess): 0: 00 48 c7 add %cl,-0x39(%rax) 3: c7 c0 4d ea 86 e8 mov $0xe886ea4d,%eax 9: 71 1f jno 0x2a b: 35 03 80 fb 01 xor $0x1fb8003,%eax 10: 48 8b 5c 24 20 mov 0x20(%rsp),%rbx 15: 0f 84 7f 04 00 00 je 0x49a 1b: e8 be 59 00 00 call 0x59de 20: 48 89 5c 24 70 mov %rbx,0x70(%rsp) 25: ff 74 24 70 push 0x70(%rsp) 29: 9d popf * 2a: 41 c6 45 22 00 movb $0x0,0x22(%r13) <-- trapping instruction 2f: 48 c7 84 24 90 01 00 movq $0x0,0x190(%rsp) 36: 00 00 00 00 00 3b: 9c pushf 3c: 8f .byte 0x8f 3d: 84 24 90 test %ah,(%rax,%rdx,4)