net: ena: avoid memory access violation by validating req_id properly

Rx req_id is an index in struct ena_eth_io_rx_cdesc_base.
The driver should validate that the Rx req_id it received from
the device is in range [0, ring_size -1].  Failure to do so could
yield to potential memory access violoation.
The validation was mistakenly done when refilling
the Rx submission queue and not in Rx completion queue.

Fixes: ad974bae ("net: ena: add support for out of order rx buffers refill")
Signed-off-by: Noam Dagan <ndagan@amazon.com>
Signed-off-by: Arthur Kiyanovski <akiyano@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/amazon/ena/ena_netdev.c

@@ -1018,13 +1018,9 @@ static int ena_refill_rx_bufs(struct ena_ring *rx_ring, u32 num)
 		struct ena_rx_buffer *rx_info;
 
 		req_id = rx_ring->free_ids[next_to_use];
-		rc = validate_rx_req_id(rx_ring, req_id);
-		if (unlikely(rc < 0))
-			break;
 
 		rx_info = &rx_ring->rx_buffer_info[req_id];
 
-
 		rc = ena_alloc_rx_page(rx_ring, rx_info,
 				       GFP_ATOMIC | __GFP_COMP);
 		if (unlikely(rc < 0)) {
@@ -1379,9 +1375,15 @@ static struct sk_buff *ena_rx_skb(struct ena_ring *rx_ring,
 	struct ena_rx_buffer *rx_info;
 	u16 len, req_id, buf = 0;
 	void *va;
+	int rc;
 
 	len = ena_bufs[buf].len;
 	req_id = ena_bufs[buf].req_id;
+
+	rc = validate_rx_req_id(rx_ring, req_id);
+	if (unlikely(rc < 0))
+		return NULL;
+
 	rx_info = &rx_ring->rx_buffer_info[req_id];
 
 	if (unlikely(!rx_info->page)) {
@@ -1454,6 +1456,11 @@ static struct sk_buff *ena_rx_skb(struct ena_ring *rx_ring,
 		buf++;
 		len = ena_bufs[buf].len;
 		req_id = ena_bufs[buf].req_id;
+
+		rc = validate_rx_req_id(rx_ring, req_id);
+		if (unlikely(rc < 0))
+			return NULL;
+
 		rx_info = &rx_ring->rx_buffer_info[req_id];
 	} while (1);