drivers: wifi: eswifi: Fix memory buffer allocation in off_read_work

When receiving data over the eswifi module, we currently read the data
first, then allocate a buffer, and finally write the data into the
buffer. The issue is that if we can't allocate the buffer, the data
that was read is lost. To fix this, we should first attempt to allocate
the buffer before reading any data. If we can't allocate the buffer, we
should not proceed with reading the data. By allocating a buffer with
the MTU size, we can read the packet, write it into the allocated buffer
and then resize by removing unused allocated buffer with
net_pkt_trim_buffer().

Signed-off-by: Léo BRIAND <[email protected]>

Author: LeoBriandFiveO

drivers/wifi/eswifi/eswifi_socket.c

@@ -133,33 +133,40 @@ static void eswifi_off_read_work(struct k_work *work)
 
 	__select_socket(eswifi, socket->index);
 
+	/* Verify if we can allocate a rx packet before reading data to prevent leaks */
+	pkt = net_pkt_rx_alloc_with_buffer(eswifi->iface, 1460,
+					   AF_UNSPEC, 0, K_NO_WAIT);
+	if (!pkt) {
+		LOG_ERR("Cannot allocate rx packet");
+		goto done;
+	}
+
 	len = __read_data(eswifi, 1460, &data); /* 1460 is max size */
 	if (len < 0) {
 		__stop_socket(eswifi, socket);
 
 		if (socket->recv_cb) {
 			/* send EOF (null pkt) */
+			net_pkt_unref(pkt);
+			pkt = NULL;
 			goto do_recv_cb;
 		}
 	}
 
 	if (!len || !socket->recv_cb) {
+		net_pkt_unref(pkt);
 		goto done;
 	}
 
 	LOG_DBG("payload sz = %d", len);
 
-	pkt = net_pkt_rx_alloc_with_buffer(eswifi->iface, len,
-					   AF_UNSPEC, 0, K_NO_WAIT);
-	if (!pkt) {
-		LOG_ERR("Cannot allocate rx packet");
-		goto done;
-	}
-
 	if (net_pkt_write(pkt, data, len) < 0) {
 		LOG_WRN("Incomplete buffer copy");
 	}
 
+	/* Resize the packet */
+	net_pkt_trim_buffer(pkt);
+
 	net_pkt_cursor_init(pkt);
 
 do_recv_cb: