netdev - Re: PROBLEM: network data corruption (bisected to e5a4b0bb803b)

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Message-Id: <201607271032.u6RAWPcS008174@sdf.org>
Date:	Wed, 27 Jul 2016 10:32:25 +0000 (UTC)
From:	Alan Curry <rlwinm@....org>
To:	Al Viro <viro@...IV.linux.org.uk>
CC:	Christian Lamparter <chunkeey@...glemail.com>,
	Alan Curry <rlwinm@....org>, linux-wireless@...r.kernel.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	alexmcwhirter@...adic.us
Subject: Re: PROBLEM: network data corruption (bisected to e5a4b0bb803b)

Al Viro wrote:
> 
> Another thing (and if that works, it's *NOT* a proper fix - it would be
> papering over the problem, but at least it would show where to look for
> it) - try (on top of mainline) the following delta:

I tried it on top of v4.6.4 and on top of the very recent v4.7-2509-g59ebc44
from Linus, and still got corruption.

> 
> diff --git a/net/core/datagram.c b/net/core/datagram.c
> index b7de71f..0ee5995 100644
> --- a/net/core/datagram.c
> +++ b/net/core/datagram.c
> @@ -734,7 +734,7 @@ int skb_copy_and_csum_datagram_msg(struct sk_buff *skb,
>  	if (!chunk)
>  		return 0;
>  
> -	if (msg_data_left(msg) < chunk) {
> +	if (iov_iter_single_seg_count(&msg->msg_iter) < chunk) {
>  		if (__skb_checksum_complete(skb))
>  			goto csum_error;
>  		if (skb_copy_datagram_msg(skb, hlen, msg, chunk))
> 

-- 
Alan Curry