netdev - Re: [SC92031] [BUG-FIX] [Patch 1/1]: Revert use of skb

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20080502144503.4ef2a430@extreme>
Date:	Fri, 2 May 2008 14:45:03 -0700
From:	Stephen Hemminger <shemminger@...tta.com>
To:	Gerrit Renker <gerrit@....abdn.ac.uk>
Cc:	davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [SC92031] [BUG-FIX] [Patch 1/1]: Revert use of skb_padto

On Fri, 2 May 2008 21:29:40 +0100
Gerrit Renker <gerrit@....abdn.ac.uk> wrote:

> [SC92031]: Revert use of skb_padto (does not update skb->len)
> 
> This reverts use of skb_padto() introduced in 
> 
>  commit 26a17b7bbb36a8552d531bc1ad08472fb5aa3007
>  Date:   Wed Apr 2 10:11:11 2008 -0700
>  sc92031: start transmit return value bugfix
> 
> The padto does not work because the driver code evaluates `len' later on
> and there are cases where skb->len is not updated accordingly.
> 
> This was observed with ARP frames (skb->len = 42 bytes, !skb_cloned(),
> skb_tailroom = 84 bytes). Then in skb_pad(), the first condition is true,
> where skb->len is not updated. As a consequence, the driver uses 42 bytes
> instead of the 60 bytes, and the ARP frame never makes it onto the wire.
> 
> Signed-off-by: Gerrit Renker <gerrit@....abdn.ac.uk>
> ---
>  sc92031.c |    8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> --- a/drivers/net/sc92031.c
> +++ b/drivers/net/sc92031.c
> @@ -953,9 +953,6 @@ static int sc92031_start_xmit(struct sk_buff *skb, struct net_device *dev)
>  	unsigned entry;
>  	u32 tx_status;
>  
> -	if (skb_padto(skb, ETH_ZLEN))
> -		return NETDEV_TX_OK;
> -
>  	if (unlikely(skb->len > TX_BUF_SIZE)) {
>  		dev->stats.tx_dropped++;
>  		goto out;
> @@ -975,6 +972,11 @@ static int sc92031_start_xmit(struct sk_buff *skb, struct net_device *dev)
>  	skb_copy_and_csum_dev(skb, priv->tx_bufs + entry * TX_BUF_SIZE);
>  
>  	len = skb->len;
> +	if (unlikely(len < ETH_ZLEN)) {
> +		memset(priv->tx_bufs + entry * TX_BUF_SIZE + len,
> +				0, ETH_ZLEN - len);
> +		len = ETH_ZLEN;
> +	}
>  

Yes, this also works better in the out of memory case since it doesn't
need to reallocate the skb.

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html