=============================== [ INFO: suspicious RCU usage. ] 4.4.174+ #4 Not tainted ------------------------------- net/ipv6/ip6_fib.c:1465 suspicious rcu_dereference_protected() usage! other info that might help us debug this: rcu_scheduler_active = 1, debug_locks = 0 4 locks held by syz-executor.1/22722: #0: (rtnl_mutex){+.+.+.}, at: [] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70 #1: (fib6_gc_lock){+.-...}, at: [] spin_trylock_bh include/linux/spinlock.h:367 [inline] #1: (fib6_gc_lock){+.-...}, at: [] fib6_run_gc+0x18c/0x230 net/ipv6/ip6_fib.c:1812 #2: (rcu_read_lock){......}, at: [] __fib6_clean_all+0x0/0x240 net/ipv6/ip6_fib.c:1698 #3: (&tb->tb6_lock){++--..}, at: [] __fib6_clean_all+0xe8/0x240 net/ipv6/ip6_fib.c:1712 stack backtrace: CPU: 1 PID: 22722 Comm: syz-executor.1 Not tainted 4.4.174+ #4 0000000000000000 255700b1a75c0439 ffff8800885a7218 ffffffff81aad1a1 ffff8801d8922c40 0000000000000000 0000000000000001 00000000000005b9 ffff8800a2b38000 ffff8800885a7248 ffffffff813ab7d6 ffff8800885a7468 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xc1/0x120 lib/dump_stack.c:51 [] lockdep_rcu_suspicious.cold+0x10a/0x149 kernel/locking/lockdep.c:4305 [] fib6_del+0x7ea/0xae0 net/ipv6/ip6_fib.c:1465 [] fib6_clean_node+0x29c/0x500 net/ipv6/ip6_fib.c:1652 [] fib6_walk_continue+0x3e0/0x630 net/ipv6/ip6_fib.c:1578 [] fib6_walk+0x91/0xe0 net/ipv6/ip6_fib.c:1623 [] fib6_clean_tree+0xe8/0x120 net/ipv6/ip6_fib.c:1697 [] __fib6_clean_all+0x100/0x240 net/ipv6/ip6_fib.c:1713 [] fib6_clean_all net/ipv6/ip6_fib.c:1724 [inline] [] fib6_run_gc+0xaf/0x230 net/ipv6/ip6_fib.c:1821 [] ndisc_netdev_event+0x2b0/0x360 net/ipv6/ndisc.c:1707 [] notifier_call_chain+0xb9/0x1e0 kernel/notifier.c:93 [] __raw_notifier_call_chain kernel/notifier.c:394 [inline] [] raw_notifier_call_chain+0x2e/0x40 kernel/notifier.c:401 [] call_netdevice_notifiers_info+0x56/0x70 net/core/dev.c:1643 [] call_netdevice_notifiers net/core/dev.c:1659 [inline] [] dev_close_many+0x2f3/0x6a0 net/core/dev.c:1452 [] rollback_registered_many+0x3a0/0x9a0 net/core/dev.c:6350 [] rollback_registered+0xf2/0x1b0 net/core/dev.c:6413 [] unregister_netdevice_queue net/core/dev.c:7363 [inline] [] unregister_netdevice_queue+0x1ae/0x230 net/core/dev.c:7356 [] unregister_netdevice include/linux/netdevice.h:2289 [inline] [] __tun_detach+0x86b/0xa50 drivers/net/tun.c:548 [] tun_detach drivers/net/tun.c:557 [inline] [] tun_chr_close+0x46/0x60 drivers/net/tun.c:2263 [] __fput+0x246/0x710 fs/file_table.c:208 [] ____fput+0x16/0x20 fs/file_table.c:244 [] task_work_run+0x202/0x2b0 kernel/task_work.c:115 [] exit_task_work include/linux/task_work.h:21 [inline] [] do_exit+0x8ea/0x2c60 kernel/exit.c:763 [] do_group_exit+0x111/0x300 kernel/exit.c:893 [] get_signal+0x517/0x1570 kernel/signal.c:2321 [] do_signal+0x9c/0x1840 arch/x86/kernel/signal.c:712 [] exit_to_usermode_loop+0x127/0x170 arch/x86/entry/common.c:184 [] prepare_exit_to_usermode arch/x86/entry/common.c:221 [inline] [] syscall_return_slowpath+0x25b/0x2e0 arch/x86/entry/common.c:286 [] int_ret_from_sys_call+0x25/0xa3