packet_diag: disclose uid value

This value is disclosed via /proc/net/packet but not via netlink messages.
The goal is to have the same level of information.
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/uapi/linux/packet_diag.h

@@ -32,6 +32,7 @@ enum {
 	PACKET_DIAG_RX_RING,
 	PACKET_DIAG_TX_RING,
 	PACKET_DIAG_FANOUT,
+	PACKET_DIAG_UID,
 
 	__PACKET_DIAG_MAX,
 };

net/packet/diag.c

@@ -125,7 +125,9 @@ static int pdiag_put_fanout(struct packet_sock *po, struct sk_buff *nlskb)
 	return ret;
 }
 
-static int sk_diag_fill(struct sock *sk, struct sk_buff *skb, struct packet_diag_req *req,
+static int sk_diag_fill(struct sock *sk, struct sk_buff *skb,
+			struct packet_diag_req *req,
+			struct user_namespace *user_ns,
 			u32 portid, u32 seq, u32 flags, int sk_ino)
 {
 	struct nlmsghdr *nlh;
@@ -147,6 +149,11 @@ static int sk_diag_fill(struct sock *sk, struct sk_buff *skb, struct packet_diag
 			pdiag_put_info(po, skb))
 		goto out_nlmsg_trim;
 
+	if ((req->pdiag_show & PACKET_SHOW_INFO) &&
+	    nla_put_u32(skb, PACKET_DIAG_UID,
+			from_kuid_munged(user_ns, sock_i_uid(sk))))
+		goto out_nlmsg_trim;
+
 	if ((req->pdiag_show & PACKET_SHOW_MCLIST) &&
 			pdiag_put_mclist(po, skb))
 		goto out_nlmsg_trim;
@@ -183,7 +190,9 @@ static int packet_diag_dump(struct sk_buff *skb, struct netlink_callback *cb)
 		if (num < s_num)
 			goto next;
 
-		if (sk_diag_fill(sk, skb, req, NETLINK_CB(cb->skb).portid,
+		if (sk_diag_fill(sk, skb, req,
+				 sk_user_ns(NETLINK_CB(cb->skb).sk),
+				 NETLINK_CB(cb->skb).portid,
 				 cb->nlh->nlmsg_seq, NLM_F_MULTI,
 				 sock_i_ino(sk)) < 0)
 			goto done;