kbuild test robot reported 2 uses of rt->from not properly accessed
using rcu_dereference:
1. add rcu_dereference_protected to rt6_remove_exception_rt and make
sure it is always called with rcu lock held.
2. change rt6_do_redirect to take a reference on 'from' when accessed
the first time so it can be used the sceond time outside of the lock
Fixes: ec7b3e64852f ("net/ipv6: Make from in rt6_info rcu protected") Reported-by: kbuild test robot <lkp@intel.com> Signed-off-by: David Ahern <dsahern@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>