ipv6: Initialize rt6_info properly in ip6_blackhole_route()

ip6_blackhole_route() does not initialize the newly allocated
rt6_info properly.  This patch:
1. Call rt6_info_init() to initialize rt6i_siblings and rt6i_uncached

2. The current rt->dst._metrics init code is incorrect:
   - 'rt->dst._metrics = ort->dst._metris' is not always safe
   - Not sure what dst_copy_metrics() is trying to do here
     considering ip6_rt_blackhole_cow_metrics() always returns
     NULL

   Fix:
   - Always do dst_copy_metrics()
   - Replace ip6_rt_blackhole_cow_metrics() with
     dst_cow_metrics_generic()

3. Mask out the RTF_PCPU bit from the newly allocated blackhole route.
   This bug triggers an oops (reported by Phil Sutter) in rt6_get_cookie().
   It is because RTF_PCPU is set while rt->dst.from is NULL.

Fixes: 790d3035c2d0 ("ipv6: Create percpu rt6_info")
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Reported-by: Phil Sutter <phil@nwl.cc>
Tested-by: Phil Sutter <phil@nwl.cc>
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Cc: Julian Anastasov <ja@ssi.bg>
Cc: Phil Sutter <phil@nwl.cc>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 4198017a5aa7ea4e4975930ccded42a0146038ed..968f31c01f89e8ccc6a4a13c056f8be3dcc0b7c6 100644 (file)
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -248,12 +248,6 @@ static void ip6_rt_blackhole_redirect(struct dst_entry *dst, struct sock *sk,
 {
 }
 
-static u32 *ip6_rt_blackhole_cow_metrics(struct dst_entry *dst,
-                                        unsigned long old)
-{
-       return NULL;
-}
-
 static struct dst_ops ip6_dst_blackhole_ops = {
        .family                 =       AF_INET6,
        .destroy                =       ip6_dst_destroy,
@@ -262,7 +256,7 @@ static struct dst_ops ip6_dst_blackhole_ops = {
        .default_advmss         =       ip6_default_advmss,
        .update_pmtu            =       ip6_rt_blackhole_update_pmtu,
        .redirect               =       ip6_rt_blackhole_redirect,
-       .cow_metrics            =       ip6_rt_blackhole_cow_metrics,
+       .cow_metrics            =       dst_cow_metrics_generic,
        .neigh_lookup           =       ip6_neigh_lookup,
 };
 
@@ -1219,24 +1213,20 @@ struct dst_entry *ip6_blackhole_route(struct net *net, struct dst_entry *dst_ori
 
        rt = dst_alloc(&ip6_dst_blackhole_ops, ort->dst.dev, 1, DST_OBSOLETE_NONE, 0);
        if (rt) {
-               new = &rt->dst;
-
-               memset(new + 1, 0, sizeof(*rt) - sizeof(*new));
+               rt6_info_init(rt);
 
+               new = &rt->dst;
                new->__use = 1;
                new->input = dst_discard;
                new->output = dst_discard_sk;
 
-               if (dst_metrics_read_only(&ort->dst))
-                       new->_metrics = ort->dst._metrics;
-               else
-                       dst_copy_metrics(new, &ort->dst);
+               dst_copy_metrics(new, &ort->dst);
                rt->rt6i_idev = ort->rt6i_idev;
                if (rt->rt6i_idev)
                        in6_dev_hold(rt->rt6i_idev);
 
                rt->rt6i_gateway = ort->rt6i_gateway;
-               rt->rt6i_flags = ort->rt6i_flags;
+               rt->rt6i_flags = ort->rt6i_flags & ~RTF_PCPU;
                rt->rt6i_metric = 0;
 
                memcpy(&rt->rt6i_dst, &ort->rt6i_dst, sizeof(struct rt6key));