RE: NULL Pointer Deference: NFS & Telnet

Arce, Abraham
2010-09-07T21:43:54Z

Eric, David,

> From: Eric Dumazet [mailto:eric.dumazet@gmail.com]

[..]

> > By increasing the allocation length of our rx skbuff the corruption issue is
> fixed... I have increased it by 2... Were we writing outside our boundaries of
> skb data?
> >
>
> Yes that makes sense, nr_frag is right after the packet (padded to L1
> cache size)
>
> But please do the correct allocation ?
>
> Also, we dont need FCS ?

FCS -> CRC is enable in hardware, under ks8851_net_open()

TXCR_TXCRC | /* add CRC */

How about the following patch? I am using added helper function:
netdev_alloc_skb_ip_align()

diff --git a/drivers/net/ks8851.c b/drivers/net/ks8851.c
index b4fb07a..df70a83 100644
--- a/drivers/net/ks8851.c
+++ b/drivers/net/ks8851.c
@@ -503,17 +503,14 @@ static void ks8851_rx_pkts(struct ks8851_net *ks)
ks8851_wrreg16(ks, KS_RXQCR,
ks->rc_rxqcr | RXQCR_SDA | RXQCR_ADRFE);

- if (rxlen > 0) {
- skb = netdev_alloc_skb(ks->netdev, rxlen + 2 + 8);
+ if (rxlen > 4) {
+ rxlen -= 4;
+ skb = netdev_alloc_skb_ip_align(ks->netdev, 2 + rxlen);
if (!skb) {
/* todo - dump frame and move on */
}

- /* two bytes to ensure ip is aligned, and four bytes
- * for the status header and 4 bytes of garbage */
- skb_reserve(skb, 2 + 4 + 4);
-
- rxpkt = skb_put(skb, rxlen - 4) - 8;
+ rxpkt = skb_put(skb, rxlen) - 8;

/* align the packet length to 4 bytes, and add 4 bytes
* as we're getting the rx status header as well */
@@ -526,7 +523,7 @@ static void ks8851_rx_pkts(struct ks8851_net *ks)
netif_rx(skb);

ks->netdev->stats.rx_packets++;
- ks->netdev->stats.rx_bytes += rxlen - 4;
+ ks->netdev->stats.rx_bytes += rxlen;
}

ks8851_wrreg16(ks, KS_RXQCR, ks->rc_rxqcr);

Best Regards
Abraham