syzbot

random: sshd: uninitialized urandom read (32 bytes read)
audit: type=1400 audit(1552224420.658:7): avc:  denied  { map } for  pid=1785 comm="syz-executor103" path="/root/syz-executor103657884" dev="sda1" ino=16481 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
netlink: 8 bytes leftover after parsing attributes in process `syz-executor103'.
=============================
WARNING: suspicious RCU usage
4.14.105+ #29 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
4 locks held by syz-executor103/1786:
 #0:  (rtnl_mutex){+.+.}, at: [<ffffffffbc2d4d14>] tun_detach drivers/net/tun.c:585 [inline]
 #0:  (rtnl_mutex){+.+.}, at: [<ffffffffbc2d4d14>] tun_chr_close+0x34/0x60 drivers/net/tun.c:2661
 #1:  (&(&net->ipv6.fib6_gc_lock)->rlock){+...}, at: [<ffffffffbcaedd7f>] spin_trylock_bh include/linux/spinlock.h:377 [inline]
 #1:  (&(&net->ipv6.fib6_gc_lock)->rlock){+...}, at: [<ffffffffbcaedd7f>] fib6_run_gc+0x1ff/0x2a0 net/ipv6/ip6_fib.c:1939
 #2:  (rcu_read_lock){....}, at: [<ffffffffbcae51b0>] __fib6_clean_all+0x0/0x230 net/ipv6/ip6_fib.c:1823
 #3:  (&tb->tb6_lock){++..}, at: [<ffffffffbcae528e>] __fib6_clean_all+0xde/0x230 net/ipv6/ip6_fib.c:1837

stack backtrace:
CPU: 0 PID: 1786 Comm: syz-executor103 Not tainted 4.14.105+ #29
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
 ndisc_netdev_event+0x32b/0x3d0 net/ipv6/ndisc.c:1779
 notifier_call_chain+0x10c/0x1a0 kernel/notifier.c:93