============================= WARNING: suspicious RCU usage 4.14.96+ #19 Not tainted ----------------------------- net/ipv6/ip6_fib.c:1590 suspicious rcu_dereference_protected() usage! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 5 locks held by syz-executor4/4301: #0: (&xt[i].mutex){+.+.}, at: [] xt_find_table_lock+0x35/0x3d0 net/netfilter/x_tables.c:1092 #1: (((&net->ipv6.ip6_fib_timer))){+.-.}, at: [] lockdep_copy_map include/linux/lockdep.h:174 [inline] #1: (((&net->ipv6.ip6_fib_timer))){+.-.}, at: [] call_timer_fn+0xc6/0x680 kernel/time/timer.c:1269 #2: (&(&net->ipv6.fib6_gc_lock)->rlock){+.-.}, at: [] spin_lock_bh include/linux/spinlock.h:322 [inline] #2: (&(&net->ipv6.fib6_gc_lock)->rlock){+.-.}, at: [] fib6_run_gc+0x93/0x2a0 net/ipv6/ip6_fib.c:1938 #3: (rcu_read_lock){....}, at: [] __fib6_clean_all+0x0/0x230 net/ipv6/ip6_fib.c:1823 #4: (&tb->tb6_lock){++--}, at: [] __fib6_clean_all+0xde/0x230 net/ipv6/ip6_fib.c:1837 stack backtrace: CPU: 1 PID: 4301 Comm: syz-executor4 Not tainted 4.14.96+ #19 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0xb9/0x10e lib/dump_stack.c:53 fib6_del+0x8c2/0xbe0 net/ipv6/ip6_fib.c:1590 fib6_clean_node+0x270/0x440 net/ipv6/ip6_fib.c:1777 fib6_walk_continue+0x3a5/0x5f0 net/ipv6/ip6_fib.c:1703 fib6_walk+0x8d/0xe0 net/ipv6/ip6_fib.c:1748 fib6_clean_tree+0xd4/0x110 net/ipv6/ip6_fib.c:1822 __fib6_clean_all+0xf5/0x230 net/ipv6/ip6_fib.c:1838 fib6_clean_all net/ipv6/ip6_fib.c:1849 [inline] fib6_run_gc+0x104/0x2a0 net/ipv6/ip6_fib.c:1947 call_timer_fn+0x14a/0x680 kernel/time/timer.c:1279 expire_timers+0x216/0x4b0 kernel/time/timer.c:1318 __run_timers kernel/time/timer.c:1634 [inline] run_timer_softirq+0x1eb/0x5d0 kernel/time/timer.c:1647 __do_softirq+0x234/0x9ca kernel/softirq.c:288 invoke_softirq kernel/softirq.c:368 [inline] irq_exit+0x114/0x150 kernel/softirq.c:409 exiting_irq arch/x86/include/asm/apic.h:648 [inline] smp_apic_timer_interrupt+0x185/0x620 arch/x86/kernel/apic/apic.c:1064 apic_timer_interrupt+0x84/0x90 arch/x86/entry/entry_64.S:787 RIP: 0010:xt_target_to_user+0x42/0x1f0 net/netfilter/x_tables.c:322 RSP: 0018:ffff8881cdc67ba8 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff10 RAX: dffffc0000000000 RBX: ffff8881ac8d9478 RCX: ffffffff94443f40 RDX: 1ffff1103591b290 RSI: 00007ffc89637d50 RDI: ffff8881ac8d9478 RBP: 00007ffc89637d50 R08: 0000000000000000 R09: fffff52000165008 R10: fffff52000165007 R11: ffffc90000b2803f R12: ffff8881ac8d9480 R13: 00000000000001c8 R14: 00007ffc89637b18 R15: ffff8881da8a7d00 copy_entries_to_user net/ipv4/netfilter/ip_tables.c:860 [inline] get_entries net/ipv4/netfilter/ip_tables.c:1025 [inline] do_ipt_get_ctl+0x624/0x790 net/ipv4/netfilter/ip_tables.c:1702 nf_sockopt net/netfilter/nf_sockopt.c:104 [inline] nf_getsockopt+0x68/0xc0 net/netfilter/nf_sockopt.c:122 ip_getsockopt net/ipv4/ip_sockglue.c:1566 [inline] ip_getsockopt+0x118/0x160 net/ipv4/ip_sockglue.c:1551 tcp_getsockopt net/ipv4/tcp.c:3235 [inline] tcp_getsockopt+0x81/0xc0 net/ipv4/tcp.c:3229 SYSC_getsockopt net/socket.c:1895 [inline] SyS_getsockopt+0x11d/0x1f0 net/socket.c:1877 do_syscall_64+0x19b/0x4b0 arch/x86/entry/common.c:289 ip6_tunnel: ip6tnl1 xmit: Local address not yet configured! netlink: 3 bytes leftover after parsing attributes in process `syz-executor3'. netlink: 3 bytes leftover after parsing attributes in process `syz-executor3'. A link change request failed with some changes committed already. Interface lo may have been left with an inconsistent configuration, please check. netlink: 3 bytes leftover after parsing attributes in process `syz-executor3'. netlink: 3 bytes leftover after parsing attributes in process `syz-executor3'. A link change request failed with some changes committed already. Interface lo may have been left with an inconsistent configuration, please check. netlink: 8 bytes leftover after parsing attributes in process `syz-executor1'. netlink: 8 bytes leftover after parsing attributes in process `syz-executor1'. audit: type=1400 audit(1548589875.978:104): avc: denied { create } for pid=25286 comm="syz-executor2" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_iscsi_socket permissive=1 ip6_tunnel: ip6tnl1 xmit: Local address not yet configured!