net: core: add UID to flows, rules, and routes

- Define a new FIB rule attributes, FRA_UID_RANGE, to describe a
  range of UIDs.
- Define a RTA_UID attribute for per-UID route lookups and dumps.
- Support passing these attributes to and from userspace via
  rtnetlink. The value INVALID_UID indicates no UID was
  specified.
- Add a UID field to the flow structures.

Signed-off-by: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 72 insertions, 2 deletions

diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
index be4629c344a6..5de436a73be2 100644
--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c
@@ -18,6 +18,11 @@
 #include <net/fib_rules.h>
 #include <net/ip_tunnels.h>
 
+static const struct fib_kuid_range fib_kuid_range_unset = {
+	KUIDT_INIT(0),
+	KUIDT_INIT(~0),
+};
+
 int fib_default_rule_add(struct fib_rules_ops *ops,
 			 u32 pref, u32 table, u32 flags)
 {
@@ -33,6 +38,7 @@ int fib_default_rule_add(struct fib_rules_ops *ops,
 	r->table = table;
 	r->flags = flags;
 	r->fr_net = ops->fro_net;
+	r->uid_range = fib_kuid_range_unset;
 
 	r->suppress_prefixlen = -1;
 	r->suppress_ifgroup = -1;
@@ -172,6 +178,34 @@ void fib_rules_unregister(struct fib_rules_ops *ops)
 }
 EXPORT_SYMBOL_GPL(fib_rules_unregister);
 
+static int uid_range_set(struct fib_kuid_range *range)
+{
+	return uid_valid(range->start) && uid_valid(range->end);
+}
+
+static struct fib_kuid_range nla_get_kuid_range(struct nlattr **tb)
+{
+	struct fib_rule_uid_range *in;
+	struct fib_kuid_range out;
+
+	in = (struct fib_rule_uid_range *)nla_data(tb[FRA_UID_RANGE]);
+
+	out.start = make_kuid(current_user_ns(), in->start);
+	out.end = make_kuid(current_user_ns(), in->end);
+
+	return out;
+}
+
+static int nla_put_uid_range(struct sk_buff *skb, struct fib_kuid_range *range)
+{
+	struct fib_rule_uid_range out = {
+		from_kuid_munged(current_user_ns(), range->start),
+		from_kuid_munged(current_user_ns(), range->end)
+	};
+
+	return nla_put(skb, FRA_UID_RANGE, sizeof(out), &out);
+}
+
 static int fib_rule_match(struct fib_rule *rule, struct fib_rules_ops *ops,
 			  struct flowi *fl, int flags,
 			  struct fib_lookup_arg *arg)
@@ -193,6 +227,10 @@ static int fib_rule_match(struct fib_rule *rule, struct fib_rules_ops *ops,
 	if (rule->l3mdev && !l3mdev_fib_rule_match(rule->fr_net, fl, arg))
 		goto out;
 
+	if (uid_lt(fl->flowi_uid, rule->uid_range.start) ||
+	    uid_gt(fl->flowi_uid, rule->uid_range.end))
+		goto out;
+
 	ret = ops->match(rule, fl, flags);
 out:
 	return (rule->flags & FIB_RULE_INVERT) ? !ret : ret;
@@ -429,6 +467,21 @@ int fib_nl_newrule(struct sk_buff *skb, struct nlmsghdr *nlh)
 	if (rule->l3mdev && rule->table)
 		goto errout_free;
 
+	if (tb[FRA_UID_RANGE]) {
+		if (current_user_ns() != net->user_ns) {
+			err = -EPERM;
+			goto errout_free;
+		}
+
+		rule->uid_range = nla_get_kuid_range(tb);
+
+		if (!uid_range_set(&rule->uid_range) ||
+		    !uid_lte(rule->uid_range.start, rule->uid_range.end))
+			goto errout_free;
+	} else {
+		rule->uid_range = fib_kuid_range_unset;
+	}
+
 	if ((nlh->nlmsg_flags & NLM_F_EXCL) &&
 	    rule_exists(ops, frh, tb, rule)) {
 		err = -EEXIST;
@@ -497,6 +550,7 @@ int fib_nl_delrule(struct sk_buff *skb, struct nlmsghdr *nlh)
 	struct fib_rules_ops *ops = NULL;
 	struct fib_rule *rule, *tmp;
 	struct nlattr *tb[FRA_MAX+1];
+	struct fib_kuid_range range;
 	int err = -EINVAL;
 
 	if (nlh->nlmsg_len < nlmsg_msg_size(sizeof(*frh)))
@@ -516,6 +570,14 @@ int fib_nl_delrule(struct sk_buff *skb, struct nlmsghdr *nlh)
 	if (err < 0)
 		goto errout;
 
+	if (tb[FRA_UID_RANGE]) {
+		range = nla_get_kuid_range(tb);
+		if (!uid_range_set(&range))
+			goto errout;
+	} else {
+		range = fib_kuid_range_unset;
+	}
+
 	list_for_each_entry(rule, &ops->rules_list, list) {
 		if (frh->action && (frh->action != rule->action))
 			continue;
@@ -552,6 +614,11 @@ int fib_nl_delrule(struct sk_buff *skb, struct nlmsghdr *nlh)
 		    (rule->l3mdev != nla_get_u8(tb[FRA_L3MDEV])))
 			continue;
 
+		if (uid_range_set(&range) &&
+		    (!uid_eq(rule->uid_range.start, range.start) ||
+		     !uid_eq(rule->uid_range.end, range.end)))
+			continue;
+
 		if (!ops->compare(rule, frh, tb))
 			continue;
 
@@ -619,7 +686,8 @@ static inline size_t fib_rule_nlmsg_size(struct fib_rules_ops *ops,
 			 + nla_total_size(4) /* FRA_SUPPRESS_IFGROUP */
 			 + nla_total_size(4) /* FRA_FWMARK */
 			 + nla_total_size(4) /* FRA_FWMASK */
-			 + nla_total_size_64bit(8); /* FRA_TUN_ID */
+			 + nla_total_size_64bit(8) /* FRA_TUN_ID */
+			 + nla_total_size(sizeof(struct fib_kuid_range));
 
 	if (ops->nlmsg_payload)
 		payload += ops->nlmsg_payload(rule);
@@ -679,7 +747,9 @@ static int fib_nl_fill_rule(struct sk_buff *skb, struct fib_rule *rule,
 	    (rule->tun_id &&
 	     nla_put_be64(skb, FRA_TUN_ID, rule->tun_id, FRA_PAD)) ||
 	    (rule->l3mdev &&
-	     nla_put_u8(skb, FRA_L3MDEV, rule->l3mdev)))
+	     nla_put_u8(skb, FRA_L3MDEV, rule->l3mdev)) ||
+	    (uid_range_set(&rule->uid_range) &&
+	     nla_put_uid_range(skb, &rule->uid_range)))
 		goto nla_put_failure;
 
 	if (rule->suppress_ifgroup != -1) {