net: ethernet: dec: tulip: Fix length mask in receive length calculation

The receive frame length calculation uses a wrong mask to calculate the
length of the received frames.

Per spec table 4-1 the length is contained in the FL (Frame Length)
field in bits 30:16.

This didn't show up as an issue so far since frames were limited to
1500 bytes which falls within the 11 bit window.

Signed-off-by: Moritz Fischer <mdf@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/dec/tulip/de2104x.c b/drivers/net/ethernet/dec/tulip/de2104x.c
index d305d1b..42b798a 100644 (file)
--- a/drivers/net/ethernet/dec/tulip/de2104x.c
+++ b/drivers/net/ethernet/dec/tulip/de2104x.c
@@ -417,7 +417,10 @@ static void de_rx (struct de_private *de)
                if (status & DescOwn)
                        break;
 
-               len = ((status >> 16) & 0x7ff) - 4;
+               /* the length is actually a 15 bit value here according
+                * to Table 4-1 in the DE2104x spec so mask is 0x7fff
+                */
+               len = ((status >> 16) & 0x7fff) - 4;
                mapping = de->rx_skb[rx_tail].mapping;
 
                if (unlikely(drop)) {