Subject: Re: Null dereference in uli526x_rx_packet()

From: Grant Grundler <[email-masked]>
Date: Sat, 28 Mar 2009 23:35:13 -0600

On Fri, Mar 27, 2009 at 11:23:32PM -0400, Kyle McMartin wrote:
> On Fri, Mar 27, 2009 at 10:47:54PM -0400, Kyle McMartin wrote:
> > > I don't know if the right fix is to return like this patch does or to set 
> > > skb = rxptr->rx_skb_ptr again.
> > > 
> > 
> > Ick... that's a good catch. I'll have to think about this.
> > 
> 
> I think this is alright, it at least keeps the original intent of the
> code. I don't pretend to have figured it out yet though.
> 
> I'll stare more at this Monday...
> 
> I guess the real question is does anyone still have one of these
> cards. I don't think I do, just the proper tulips. :/

Ditto. AFAIK, I only have tulips.

Patch below looks right to me. Clobbering the skb is certainly wrong.

Acked-by: Grant Grundler <[email-masked]>

thanks,
grant

> diff --git a/drivers/net/tulip/uli526x.c b/drivers/net/tulip/uli526x.c
> index 030e02e..9264a58 100644
> --- a/drivers/net/tulip/uli526x.c
> +++ b/drivers/net/tulip/uli526x.c
> @@ -840,13 +840,15 @@ static void uli526x_rx_packet(struct net_device *dev, struct uli526x_board_info
>  
>  			if ( !(rdes0 & 0x8000) ||
>  				((db->cr6_data & CR6_PM) && (rxlen>6)) ) {
> +				struct sk_buff *new_skb = NULL;
> +
>  				skb = rxptr->rx_skb_ptr;
>  
>  				/* Good packet, send to upper layer */
>  				/* Shorst packet used new SKB */
> -				if ( (rxlen < RX_COPY_SIZE) &&
> -					( (skb = dev_alloc_skb(rxlen + 2) )
> -					!= NULL) ) {
> +				if ((rxlen < RX_COPY_SIZE) &&
> +				    ((new_skb = dev_alloc_skb(rxlen + 2) != NULL))) {
> +					skb = new_skb;
>  					/* size less than COPY_SIZE, allocate a rxlen SKB */
>  					skb_reserve(skb, 2); /* 16byte align */
>  					memcpy(skb_put(skb, rxlen),