tree f4bf4d0471b7d5c75c21f5990fecac90fdb1f57d
parent bbd63f06d114a52be33f6982fc89ca2768cdeb62
author Wei Wang <weiwan@google.com> 1507316768 -0700
committer David S. Miller <davem@davemloft.net> 1507407778 +0100

ipv6: check fn->leaf before it is used

If rwlock is replaced with rcu and spinlock, it is possible that the
reader thread will see fn->leaf as NULL in the following scenarios:
1. fib6_add() is in progress and we have already inserted a new node but
not yet inserted the route.
2. fib6_del_route() is in progress and we have already set fn->leaf to
NULL but not yet freed the node because of rcu grace period.

This patch makes sure all the reader threads check fn->leaf first before
using it. And together with later patch to grab rcu_read_lock() and
rcu_dereference() fn->leaf, it makes sure reader threads are safe when
accessing fn->leaf.

Signed-off-by: Wei Wang <weiwan@google.com>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>