netfilter: xt_socket: fix broken v0 support

commit 681f130f39e10 ("netfilter: xt_socket: add XT_SOCKET_NOWILDCARD
flag") added a potential NULL dereference if an old iptables package
uses v0 of the match.

Fix this by removing the test on @info in fast path.

IPv6 can remove the test as well, as it uses v1 or v2.

Reported-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Patrick McHardy <kaber@trash.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 7 insertions, 3 deletions

diff --git a/net/netfilter/xt_socket.c b/net/netfilter/xt_socket.c
index f8b71911037a..20b15916f403 100644
--- a/net/netfilter/xt_socket.c
+++ b/net/netfilter/xt_socket.c
@@ -172,7 +172,7 @@ socket_match(const struct sk_buff *skb, struct xt_action_param *par,
 
                 /* Ignore non-transparent sockets,
                    if XT_SOCKET_TRANSPARENT is used */
-                if (info && info->flags & XT_SOCKET_TRANSPARENT)
+                if (info->flags & XT_SOCKET_TRANSPARENT)
                         transparent = ((sk->sk_state != TCP_TIME_WAIT &&
                                         inet_sk(sk)->transparent) ||
                                        (sk->sk_state == TCP_TIME_WAIT &&
@@ -196,7 +196,11 @@ socket_match(const struct sk_buff *skb, struct xt_action_param *par,
 static bool
 socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par)
 {
-        return socket_match(skb, par, NULL);
+        static struct xt_socket_mtinfo1 xt_info_v0 = {
+                .flags = 0,
+        };
+
+        return socket_match(skb, par, &xt_info_v0);
 }
 
 static bool
@@ -314,7 +318,7 @@ socket_mt6_v1_v2(const struct sk_buff *skb, struct xt_action_param *par)
 
                 /* Ignore non-transparent sockets,
                    if XT_SOCKET_TRANSPARENT is used */
-                if (info && info->flags & XT_SOCKET_TRANSPARENT)
+                if (info->flags & XT_SOCKET_TRANSPARENT)
                         transparent = ((sk->sk_state != TCP_TIME_WAIT &&
                                         inet_sk(sk)->transparent) ||
                                        (sk->sk_state == TCP_TIME_WAIT &&