ipv4: Don't override return code from ip_route_input_noref()

After ip_route_input() calls ip_route_input_noref(), another
check on skb_dst() is done, but if this fails, we shouldn't
override the return code from ip_route_input_noref(), as it
could have been more specific (i.e. -EHOSTUNREACH).

This also saves one call to skb_dst_force_safe() and one to
skb_dst() in case the ip_route_input_noref() check fails.

Reported-by: Sabrina Dubroca <sdubroca@redhat.com>
Fixes: 9df16efadd2a ("ipv4: call dst_hold_safe() properly")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Acked-by: Wei Wang <weiwan@google.com>
Acked-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 3 deletions

diff --git a/include/net/route.h b/include/net/route.h
index cb0a76d9dde1..1b09a9368c68 100644
--- a/include/net/route.h
+++ b/include/net/route.h
@@ -189,10 +189,11 @@ static inline int ip_route_input(struct sk_buff *skb, __be32 dst, __be32 src,
 
         rcu_read_lock();
         err = ip_route_input_noref(skb, dst, src, tos, devin);
-        if (!err)
+        if (!err) {
                 skb_dst_force_safe(skb);
-        if (!skb_dst(skb))
-                err = -EINVAL;
+                if (!skb_dst(skb))
+                        err = -EINVAL;
+        }
         rcu_read_unlock();
 
         return err;