userns: xt_owner: Add basic user namespace support.

- Only allow adding matches from the initial user namespace
- Add the appropriate conversion functions to handle matches
  against sockets in other user namespaces.

Cc: Jan Engelhardt <jengelh@medozas.de>
Cc: Patrick McHardy <kaber@trash.net>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

2 files changed, 24 insertions, 7 deletions

diff --git a/init/Kconfig b/init/Kconfig
index 40f50204dddb..76ffca9729b3 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -943,7 +943,6 @@ config UIDGID_CONVERTED
 
         # Networking
         depends on NET_9P = n
-        depends on NETFILTER_XT_MATCH_OWNER = n
         depends on AF_RXRPC = n
         depends on NET_KEY = n
         depends on DNS_RESOLVER = n
diff --git a/net/netfilter/xt_owner.c b/net/netfilter/xt_owner.c
index 772d7389b337..ca2e577ed8ac 100644
--- a/net/netfilter/xt_owner.c
+++ b/net/netfilter/xt_owner.c
@@ -17,6 +17,17 @@
 #include <linux/netfilter/x_tables.h>
 #include <linux/netfilter/xt_owner.h>
 
+static int owner_check(const struct xt_mtchk_param *par)
+{
+        struct xt_owner_match_info *info = par->matchinfo;
+
+        /* For now only allow adding matches from the initial user namespace */
+        if ((info->match & (XT_OWNER_UID|XT_OWNER_GID)) &&
+            (current_user_ns() != &init_user_ns))
+                return -EINVAL;
+        return 0;
+}
+
 static bool
 owner_mt(const struct sk_buff *skb, struct xt_action_param *par)
 {
@@ -37,17 +48,23 @@ owner_mt(const struct sk_buff *skb, struct xt_action_param *par)
                 return ((info->match ^ info->invert) &
                        (XT_OWNER_UID | XT_OWNER_GID)) == 0;
 
-        if (info->match & XT_OWNER_UID)
-                if ((filp->f_cred->fsuid >= info->uid_min &&
-                    filp->f_cred->fsuid <= info->uid_max) ^
+        if (info->match & XT_OWNER_UID) {
+                kuid_t uid_min = make_kuid(&init_user_ns, info->uid_min);
+                kuid_t uid_max = make_kuid(&init_user_ns, info->uid_max);
+                if ((uid_gte(filp->f_cred->fsuid, uid_min) &&
+                     uid_lte(filp->f_cred->fsuid, uid_max)) ^
                     !(info->invert & XT_OWNER_UID))
                         return false;
+        }
 
-        if (info->match & XT_OWNER_GID)
-                if ((filp->f_cred->fsgid >= info->gid_min &&
-                    filp->f_cred->fsgid <= info->gid_max) ^
+        if (info->match & XT_OWNER_GID) {
+                kgid_t gid_min = make_kgid(&init_user_ns, info->gid_min);
+                kgid_t gid_max = make_kgid(&init_user_ns, info->gid_max);
+                if ((gid_gte(filp->f_cred->fsgid, gid_min) &&
+                     gid_lte(filp->f_cred->fsgid, gid_max)) ^
                     !(info->invert & XT_OWNER_GID))
                         return false;
+        }
 
         return true;
 }
@@ -56,6 +73,7 @@ static struct xt_match owner_mt_reg __read_mostly = {
         .name       = "owner",
         .revision   = 1,
         .family     = NFPROTO_UNSPEC,
+        .checkentry = owner_check,
         .match      = owner_mt,
         .matchsize  = sizeof(struct xt_owner_match_info),
         .hooks      = (1 << NF_INET_LOCAL_OUT) |