linux-kernel - Re: [RFC PATCH 2/6] virtio/console: Add a failback for unstealable pipe buffer

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Date:	Thu, 9 Aug 2012 11:24:46 +0200
From:	Borislav Petkov <bp@...64.org>
To:	Amit Shah <amit.shah@...hat.com>
Cc:	Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@...achi.com>,
	linux-kernel@...r.kernel.org,
	Anthony Liguori <anthony@...emonkey.ws>,
	Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...64.org>,
	"Franch Ch. Eigler" <fche@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Herbert Xu <herbert@...dor.hengli.com.au>,
	Ingo Molnar <mingo@...hat.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	virtualization@...ts.linux-foundation.org, qemu-devel@...gnu.org,
	yrl.pp-manager.tt@...achi.com,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Subject: Re: [RFC PATCH 2/6] virtio/console: Add a failback for unstealable
 pipe buffer

On Thu, Aug 09, 2012 at 02:33:12PM +0530, Amit Shah wrote:
> > @@ -807,9 +807,31 @@ static int pipe_to_sg(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
> >  
> >  		len = min(buf->len, sd->len);
> >  		sg_set_page(&(sgl->sg[sgl->n]), buf->page, len, buf->offset);
> > -		sgl->n++;
> > -		sgl->len += len;
> > +	} else {
> > +		/* Failback to copying a page */
> > +		struct page *page = alloc_page(GFP_KERNEL);
> 
> I prefer zeroing out the page.  If there's not enough data to be
> filled in the page, the remaining data can be leaked to the host.

get_zeroed_page()?

-- 
Regards/Gruss,
Boris.

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