Bluetooth: hci_sock: Forward credentials to monitor

This stores scm_creds into hci_skb_cb so they can be properly forwarded
to the likes of btmon which is then able to print information about the
process who is originating the traffic:

bluetoothd[35]: @ MGMT Command: Rea.. (0x0001) plen 0  {0x0001}
@ MGMT Event: Command Complete (0x0001) plen 6         {0x0001}
      Read Management Version Information (0x0001) plen 3

bluetoothd[35]: < ACL Data T.. flags 0x00 dlen 41
      ATT: Write Command (0x52) len 36
        Handle: 0x0043 Type: ASE Control Point (0x2bc6)
          Data: 020203000110270000022800020a00409c0001000110270000022800020a00409c00
            Opcode: QoS Configuration (0x02)
            Number of ASE(s): 2
            ASE: #0
            ASE ID: 0x03
            CIG ID: 0x00
            CIS ID: 0x01
            SDU Interval: 10000 usec
            Framing: Unframed (0x00)
            PHY: 0x02
            LE 2M PHY (0x02)
            Max SDU: 40
            RTN: 2
            Max Transport Latency: 10
            Presentation Delay: 40000 us
            ASE: #1
            ASE ID: 0x01
            CIG ID: 0x00
            CIS ID: 0x01
            SDU Interval: 10000 usec
            Framing: Unframed (0x00)
            PHY: 0x02
            LE 2M PHY (0x02)
            Max SDU: 40
            RTN: 2
            Max Transport Latency: 10
            Presentation Delay: 40000 us
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

include/net/bluetooth/bluetooth.h

@@ -471,6 +471,7 @@ struct bt_skb_cb {
 		struct sco_ctrl sco;
 		struct hci_ctrl hci;
 		struct mgmt_ctrl mgmt;
+		struct scm_creds creds;
 	};
 };
 #define bt_cb(skb) ((struct bt_skb_cb *)((skb)->cb))

net/bluetooth/hci_sock.c

@@ -264,6 +264,53 @@ void hci_send_to_sock(struct hci_dev *hdev, struct sk_buff *skb)
 	kfree_skb(skb_copy);
 }
 
+static void hci_sock_copy_creds(struct sock *sk, struct sk_buff *skb)
+{
+	struct scm_creds *creds;
+
+	if (!sk || WARN_ON(!skb))
+		return;
+
+	creds = &bt_cb(skb)->creds;
+
+	/* Check if peer credentials is set */
+	if (!sk->sk_peer_pid) {
+		/* Check if parent peer credentials is set */
+		if (bt_sk(sk)->parent && bt_sk(sk)->parent->sk_peer_pid)
+			sk = bt_sk(sk)->parent;
+		else
+			return;
+	}
+
+	/* Check if scm_creds already set */
+	if (creds->pid == pid_vnr(sk->sk_peer_pid))
+		return;
+
+	memset(creds, 0, sizeof(*creds));
+
+	creds->pid = pid_vnr(sk->sk_peer_pid);
+	if (sk->sk_peer_cred) {
+		creds->uid = sk->sk_peer_cred->uid;
+		creds->gid = sk->sk_peer_cred->gid;
+	}
+}
+
+static struct sk_buff *hci_skb_clone(struct sk_buff *skb)
+{
+	struct sk_buff *nskb;
+
+	if (!skb)
+		return NULL;
+
+	nskb = skb_clone(skb, GFP_ATOMIC);
+	if (!nskb)
+		return NULL;
+
+	hci_sock_copy_creds(skb->sk, nskb);
+
+	return nskb;
+}
+
 /* Send frame to sockets with specific channel */
 static void __hci_send_to_channel(unsigned short channel, struct sk_buff *skb,
 				  int flag, struct sock *skip_sk)
@@ -289,7 +336,7 @@ static void __hci_send_to_channel(unsigned short channel, struct sk_buff *skb,
 		if (hci_pi(sk)->channel != channel)
 			continue;
 
-		nskb = skb_clone(skb, GFP_ATOMIC);
+		nskb = hci_skb_clone(skb);
 		if (!nskb)
 			continue;
 
@@ -356,6 +403,8 @@ void hci_send_to_monitor(struct hci_dev *hdev, struct sk_buff *skb)
 	if (!skb_copy)
 		return;
 
+	hci_sock_copy_creds(skb->sk, skb_copy);
+
 	/* Put header before the data */
 	hdr = skb_push(skb_copy, HCI_MON_HDR_SIZE);
 	hdr->opcode = opcode;
@@ -531,10 +580,12 @@ static struct sk_buff *create_monitor_ctrl_open(struct sock *sk)
 		return NULL;
 	}
 
-	skb = bt_skb_alloc(14 + TASK_COMM_LEN , GFP_ATOMIC);
+	skb = bt_skb_alloc(14 + TASK_COMM_LEN, GFP_ATOMIC);
 	if (!skb)
 		return NULL;
 
+	hci_sock_copy_creds(sk, skb);
+
 	flags = hci_sock_test_flag(sk, HCI_SOCK_TRUSTED) ? 0x1 : 0x0;
 
 	put_unaligned_le32(hci_pi(sk)->cookie, skb_put(skb, 4));
@@ -580,6 +631,8 @@ static struct sk_buff *create_monitor_ctrl_close(struct sock *sk)
 	if (!skb)
 		return NULL;
 
+	hci_sock_copy_creds(sk, skb);
+
 	put_unaligned_le32(hci_pi(sk)->cookie, skb_put(skb, 4));
 
 	__net_timestamp(skb);
@@ -606,6 +659,8 @@ static struct sk_buff *create_monitor_ctrl_command(struct sock *sk, u16 index,
 	if (!skb)
 		return NULL;
 
+	hci_sock_copy_creds(sk, skb);
+
 	put_unaligned_le32(hci_pi(sk)->cookie, skb_put(skb, 4));
 	put_unaligned_le16(opcode, skb_put(skb, 2));
 
@@ -638,6 +693,8 @@ send_monitor_note(struct sock *sk, const char *fmt, ...)
 	if (!skb)
 		return;
 
+	hci_sock_copy_creds(sk, skb);
+
 	va_start(args, fmt);
 	vsprintf(skb_put(skb, len), fmt, args);
 	*(u8 *)skb_put(skb, 1) = 0;
@@ -1494,6 +1551,7 @@ static void hci_sock_cmsg(struct sock *sk, struct msghdr *msg,
 static int hci_sock_recvmsg(struct socket *sock, struct msghdr *msg,
 			    size_t len, int flags)
 {
+	struct scm_cookie scm;
 	struct sock *sk = sock->sk;
 	struct sk_buff *skb;
 	int copied, err;
@@ -1538,11 +1596,16 @@ static int hci_sock_recvmsg(struct socket *sock, struct msghdr *msg,
 		break;
 	}
 
+	memset(&scm, 0, sizeof(scm));
+	scm.creds = bt_cb(skb)->creds;
+
 	skb_free_datagram(sk, skb);
 
 	if (flags & MSG_TRUNC)
 		copied = skblen;
 
+	scm_recv(sock, msg, &scm, flags);
+
 	return err ? : copied;
 }