ipv4: add missing initialization for flowi4_uid

Avoid matching of random stack value for uid when rules
are looked up on input route or when RP filter is used.
Problem should affect only setups that use ip rules with
uid range.

Fixes: 622ec2c ("net: core: add UID to flows, rules, and routes")
Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: Julian Anastasov

net/ipv4/fib_frontend.c

@@ -319,7 +319,7 @@ static int __fib_validate_source(struct sk_buff *skb, __be32 src, __be32 dst,
 	int ret, no_addr;
 	struct fib_result res;
 	struct flowi4 fl4;
-	struct net *net;
+	struct net *net = dev_net(dev);
 	bool dev_match;
 
 	fl4.flowi4_oif = 0;
@@ -332,20 +332,20 @@ static int __fib_validate_source(struct sk_buff *skb, __be32 src, __be32 dst,
 	fl4.flowi4_scope = RT_SCOPE_UNIVERSE;
 	fl4.flowi4_tun_key.tun_id = 0;
 	fl4.flowi4_flags = 0;
+	fl4.flowi4_uid = sock_net_uid(net, NULL);
 
 	no_addr = idev->ifa_list == NULL;
 
 	fl4.flowi4_mark = IN_DEV_SRC_VMARK(idev) ? skb->mark : 0;
 
 	trace_fib_validate_source(dev, &fl4);
 
-	net = dev_net(dev);
 	if (fib_lookup(net, &fl4, &res, 0))
 		goto last_resort;
 	if (res.type != RTN_UNICAST &&
 	    (res.type != RTN_LOCAL || !IN_DEV_ACCEPT_LOCAL(idev)))
 		goto e_inval;
-	if (!rpf && !fib_num_tclassid_users(dev_net(dev)) &&
+	if (!rpf && !fib_num_tclassid_users(net) &&
 	    (dev->ifindex != oif || !IN_DEV_TX_REDIRECTS(idev)))
 		goto last_resort;
 	fib_combine_itag(itag, &res);

net/ipv4/route.c

@@ -1876,6 +1876,7 @@ static int ip_route_input_slow(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 	fl4.flowi4_flags = 0;
 	fl4.daddr = daddr;
 	fl4.saddr = saddr;
+	fl4.flowi4_uid = sock_net_uid(net, NULL);
 	err = fib_lookup(net, &fl4, &res, 0);
 	if (err != 0) {
 		if (!IN_DEV_FORWARD(in_dev))