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: d52d3997f843 ("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>

1 files changed, 5 insertions, 15 deletions

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 4198017a5aa7..968f31c01f89 100644
--- 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));