[IPv4]: Convert route get to new netlink api

Fixes various unvalidated netlink attributes causing memory
corruptions when left empty by userspace applications.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 46 insertions, 40 deletions

diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index d537c933abe3..d0abeab16e66 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -453,7 +453,7 @@ int ip_rt_ioctl(unsigned int cmd, void *arg)
 
 #endif
 
-static struct nla_policy rtm_ipv4_policy[RTA_MAX+1] __read_mostly = {
+struct nla_policy rtm_ipv4_policy[RTA_MAX+1] __read_mostly = {
         [RTA_DST]               = { .type = NLA_U32 },
         [RTA_SRC]               = { .type = NLA_U32 },
         [RTA_IIF]               = { .type = NLA_U32 },
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 31b67059ac29..a4d4cb85a16c 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2737,18 +2737,24 @@ nla_put_failure:
 
 int inet_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr* nlh, void *arg)
 {
-        struct rtattr **rta = arg;
-        struct rtmsg *rtm = NLMSG_DATA(nlh);
+        struct rtmsg *rtm;
+        struct nlattr *tb[RTA_MAX+1];
         struct rtable *rt = NULL;
-        u32 dst = 0;
-        u32 src = 0;
-        int iif = 0;
-        int err = -ENOBUFS;
+        u32 dst, src, iif;
+        int err;
         struct sk_buff *skb;
 
+        err = nlmsg_parse(nlh, sizeof(*rtm), tb, RTA_MAX, rtm_ipv4_policy);
+        if (err < 0)
+                goto errout;
+
+        rtm = nlmsg_data(nlh);
+
         skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL);
-        if (!skb)
-                goto out;
+        if (skb == NULL) {
+                err = -ENOBUFS;
+                goto errout;
+        }
 
         /* Reserve room for dummy headers, this skb can pass
            through good chunk of routing engine.
@@ -2759,61 +2765,61 @@ int inet_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr* nlh, void *arg)
         skb->nh.iph->protocol = IPPROTO_ICMP;
         skb_reserve(skb, MAX_HEADER + sizeof(struct iphdr));
 
-        if (rta[RTA_SRC - 1])
-                memcpy(&src, RTA_DATA(rta[RTA_SRC - 1]), 4);
-        if (rta[RTA_DST - 1])
-                memcpy(&dst, RTA_DATA(rta[RTA_DST - 1]), 4);
-        if (rta[RTA_IIF - 1])
-                memcpy(&iif, RTA_DATA(rta[RTA_IIF - 1]), sizeof(int));
+        src = tb[RTA_SRC] ? nla_get_u32(tb[RTA_SRC]) : 0;
+        dst = tb[RTA_DST] ? nla_get_u32(tb[RTA_DST]) : 0;
+        iif = tb[RTA_IIF] ? nla_get_u32(tb[RTA_IIF]) : 0;
 
         if (iif) {
-                struct net_device *dev = __dev_get_by_index(iif);
-                err = -ENODEV;
-                if (!dev)
-                        goto out_free;
+                struct net_device *dev;
+
+                dev = __dev_get_by_index(iif);
+                if (dev == NULL) {
+                        err = -ENODEV;
+                        goto errout_free;
+                }
+
                 skb->protocol   = htons(ETH_P_IP);
                 skb->dev        = dev;
                 local_bh_disable();
                 err = ip_route_input(skb, dst, src, rtm->rtm_tos, dev);
                 local_bh_enable();
-                rt = (struct rtable*)skb->dst;
-                if (!err && rt->u.dst.error)
+
+                rt = (struct rtable*) skb->dst;
+                if (err == 0 && rt->u.dst.error)
                         err = -rt->u.dst.error;
         } else {
-                struct flowi fl = { .nl_u = { .ip4_u = { .daddr = dst,
-                                                         .saddr = src,
-                                                         .tos = rtm->rtm_tos } } };
-                int oif = 0;
-                if (rta[RTA_OIF - 1])
-                        memcpy(&oif, RTA_DATA(rta[RTA_OIF - 1]), sizeof(int));
-                fl.oif = oif;
+                struct flowi fl = {
+                        .nl_u = {
+                                .ip4_u = {
+                                        .daddr = dst,
+                                        .saddr = src,
+                                        .tos = rtm->rtm_tos,
+                                },
+                        },
+                        .oif = tb[RTA_OIF] ? nla_get_u32(tb[RTA_OIF]) : 0,
+                };
                 err = ip_route_output_key(&rt, &fl);
         }
+
         if (err)
-                goto out_free;
+                goto errout_free;
 
         skb->dst = &rt->u.dst;
         if (rtm->rtm_flags & RTM_F_NOTIFY)
                 rt->rt_flags |= RTCF_NOTIFY;
 
-        NETLINK_CB(skb).dst_pid = NETLINK_CB(in_skb).pid;
-
         err = rt_fill_info(skb, NETLINK_CB(in_skb).pid, nlh->nlmsg_seq,
                                 RTM_NEWROUTE, 0, 0);
-        if (!err)
-                goto out_free;
-        if (err < 0) {
-                err = -EMSGSIZE;
-                goto out_free;
-        }
+        if (err <= 0)
+                goto errout_free;
 
         err = rtnl_unicast(skb, NETLINK_CB(in_skb).pid);
-out:
+errout:
         return err;
 
-out_free:
+errout_free:
         kfree_skb(skb);
-        goto out;
+        goto errout;
 }
 
 int ip_rt_dump(struct sk_buff *skb,  struct netlink_callback *cb)