netdev - Re: Bug in computing data_len in tcp

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Message-ID: <1322710962.2577.3.camel@edumazet-laptop>
Date:	Thu, 01 Dec 2011 04:42:42 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Tom Herbert <therbert@...gle.com>
Cc:	Linux Netdev List <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>
Subject: Re: Bug in computing data_len in tcp_sendmsg?

Le mercredi 30 novembre 2011 à 17:48 -0800, Tom Herbert a écrit :
> I believe that skb->data_len might no be computed correctly in
> tcp_sendmsg.  Specifically, when skb_add_data_nocache (or
> skb_add_data) is called skb->data_len is not updated (skb_put only
> updates skb->len).  This results in the datalen in the head skbuf
> being zero so any subsequent uses of the value lead to incorrect
> results.  For instance, skb_headlen returns the length of the head
> skbu data and not just that of the headers.  If I'm reading this
> correctly, it's a pretty fundamental bug.
> 
> I don't have a fix for this yet.
> 
> Tom

On which tree do you see a problem ?

For example net-next seems fine to me :


static inline int skb_copy_to_page_nocache(struct sock *sk, char __user *from,
                                           struct sk_buff *skb,
                                           struct page *page,
                                           int off, int copy)
{
        int err;

        err = skb_do_copy_data_nocache(sk, skb, from, page_address(page) + off,
                                       copy, skb->len);
        if (err)
                return err;

        skb->len             += copy;
        skb->data_len        += copy;
        skb->truesize        += copy;
        sk->sk_wmem_queued   += copy;
        sk_mem_charge(sk, copy);
        return 0;
}


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