userns: Convert xt_LOG to print socket kuids and kgids as uids and gids

xt_LOG always writes messages via sb_add via printk.  Therefore when
xt_LOG logs the uid and gid of a socket a packet came from the
values should be converted to be in the initial user namespace.

Thus making xt_LOG as user namespace safe as possible.

Cc: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: Patrick McHardy <kaber@trash.net>
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, 10 insertions, 7 deletions

diff --git a/init/Kconfig b/init/Kconfig
index b44c3a390699..c8911eb6d500 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -945,7 +945,6 @@ config UIDGID_CONVERTED
         depends on NET_9P = n
         depends on NETFILTER_XT_MATCH_OWNER = n
         depends on NETFILTER_XT_MATCH_RECENT = n
-        depends on NETFILTER_XT_TARGET_LOG = n
         depends on AF_RXRPC = n
         depends on NET_KEY = n
         depends on DNS_RESOLVER = n
diff --git a/net/netfilter/xt_LOG.c b/net/netfilter/xt_LOG.c
index ff5f75fddb15..02a2bf49dcbd 100644
--- a/net/netfilter/xt_LOG.c
+++ b/net/netfilter/xt_LOG.c
@@ -363,10 +363,12 @@ static void dump_ipv4_packet(struct sbuff *m,
         /* Max length: 15 "UID=4294967295 " */
         if ((logflags & XT_LOG_UID) && !iphoff && skb->sk) {
                 read_lock_bh(&skb->sk->sk_callback_lock);
-                if (skb->sk->sk_socket && skb->sk->sk_socket->file)
+                if (skb->sk->sk_socket && skb->sk->sk_socket->file) {
+                        const struct cred *cred = skb->sk->sk_socket->file->f_cred;
                         sb_add(m, "UID=%u GID=%u ",
-                                skb->sk->sk_socket->file->f_cred->fsuid,
-                                skb->sk->sk_socket->file->f_cred->fsgid);
+                                from_kuid_munged(&init_user_ns, cred->fsuid),
+                                from_kgid_munged(&init_user_ns, cred->fsgid));
+                }
                 read_unlock_bh(&skb->sk->sk_callback_lock);
         }
 
@@ -719,10 +721,12 @@ static void dump_ipv6_packet(struct sbuff *m,
         /* Max length: 15 "UID=4294967295 " */
         if ((logflags & XT_LOG_UID) && recurse && skb->sk) {
                 read_lock_bh(&skb->sk->sk_callback_lock);
-                if (skb->sk->sk_socket && skb->sk->sk_socket->file)
+                if (skb->sk->sk_socket && skb->sk->sk_socket->file) {
+                        const struct cred *cred = skb->sk->sk_socket->file->f_cred;
                         sb_add(m, "UID=%u GID=%u ",
-                                skb->sk->sk_socket->file->f_cred->fsuid,
-                                skb->sk->sk_socket->file->f_cred->fsgid);
+                                from_kuid_munged(&init_user_ns, cred->fsuid),
+                                from_kgid_munged(&init_user_ns, cred->fsgid));
+                }
                 read_unlock_bh(&skb->sk->sk_callback_lock);
         }