netdev - Re: [PATCH] TX_RING and packet mmap

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Message-ID: <20090412142451.GA2694@ioremap.net>
Date:	Sun, 12 Apr 2009 18:24:51 +0400
From:	Evgeniy Polyakov <zbr@...emap.net>
To:	Johann Baudy <johann.baudy@...-log.net>
Cc:	Herbert Xu <herbert@...dor.apana.org.au>, netdev@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>,
	Patrick McHardy <kaber@...sh.net>, jamal <hadi@...erus.ca>
Subject: Re: [PATCH] TX_RING and packet mmap

On Sun, Apr 12, 2009 at 01:23:30PM +0200, Johann Baudy (johann.baudy@...-log.net) wrote:
> > Page itself will live until destruction time, when skb is linearized
> > page is freed, so your own destructor will find that given page is no
> > longer used, and appropriate memory area can be overwritten.
> Ok, so if my understanding is correct, fragment data is copied, frags
> info (page, offset, size ...) of  skb_shinfo(skb) remain available and
> skb->data_len is equal to 0 (to tag it as linear).
> Then I can use address of skb_shinfo(n)->frags[0].page to derive my
> header whatever sending path.

No, I was wrong, linearization may silently put pages without calling a
destructor.

-- 
	Evgeniy Polyakov
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