ipv6: fix incorrect route 'expires' value passed to userspace

When userspace use RTM_GETROUTE to dump route table, with an already
expired route entry, we always got an 'expires' value(2147157)
calculated base on INT_MAX.

The reason of this problem is in the following satement:
	rt->dst.expires - jiffies < INT_MAX
gcc promoted the type of both sides of '<' to unsigned long, thus
a small negative value would be considered greater than INT_MAX.

With the help of Eric Dumazet, do the out of bound checks in
rtnl_put_cacheinfo(), _after_ conversion to clock_t.

Signed-off-by: Li Wei <lw@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 8 insertions, 8 deletions

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index bc9e380f0abf..5ff949dc954f 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -625,9 +625,13 @@ int rtnl_put_cacheinfo(struct sk_buff *skb, struct dst_entry *dst, u32 id,
                 .rta_id =  id,
         };
 
-        if (expires)
-                ci.rta_expires = jiffies_to_clock_t(expires);
+        if (expires) {
+                unsigned long clock;
 
+                clock = jiffies_to_clock_t(abs(expires));
+                clock = min_t(unsigned long, clock, INT_MAX);
+                ci.rta_expires = (expires > 0) ? clock : -clock;
+        }
         return nla_put(skb, RTA_CACHEINFO, sizeof(ci), &ci);
 }
 EXPORT_SYMBOL_GPL(rtnl_put_cacheinfo);
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index cf02cb97bbdd..8e80fd279100 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2480,12 +2480,8 @@ static int rt6_fill_node(struct net *net,
                 goto nla_put_failure;
         if (nla_put_u32(skb, RTA_PRIORITY, rt->rt6i_metric))
                 goto nla_put_failure;
-        if (!(rt->rt6i_flags & RTF_EXPIRES))
-                expires = 0;
-        else if (rt->dst.expires - jiffies < INT_MAX)
-                expires = rt->dst.expires - jiffies;
-        else
-                expires = INT_MAX;
+
+        expires = (rt->rt6i_flags & RTF_EXPIRES) ? rt->dst.expires - jiffies : 0;
 
         if (rtnl_put_cacheinfo(skb, &rt->dst, 0, expires, rt->dst.error) < 0)
                 goto nla_put_failure;