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) {