net: vmw_vsock: vmci: Check memcpy_from_msg()

vmci_transport_dgram_enqueue() does not check the return value
of memcpy_from_msg(). If memcpy_from_msg() fails, it is possible that
uninitialized memory contents are sent unintentionally instead of user's
message in the datagram to the destination. Return with an error if
memcpy_from_msg() fails.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 0f7db23a07af ("vmci_transport: switch ->enqeue_dgram, ->enqueue_stream and ->dequeue_stream to msghdr")
Signed-off-by: Artem Chernyshev <[e-mail]>
Reviewed-by: Stefano Garzarella <[e-mail]>
Reviewed-by: Vishnu Dasa <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/vmw_vsock/vmci_transport.c

···
 	if (!dg)
 		return -ENOMEM;
 
-	memcpy_from_msg(VMCI_DG_PAYLOAD(dg), msg, len);
+	err = memcpy_from_msg(VMCI_DG_PAYLOAD(dg), msg, len);
+	if (err) {
+		kfree(dg);
+		return err;
+	}
 
 	dg->dst = vmci_make_handle(remote_addr->svm_cid,
 				   remote_addr->svm_port);