linux-kernel - Re: [patch 1/9] fs: libfs buffered write leak fix

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Message-Id: <20070202175801.3f97f79b.akpm@linux-foundation.org>
Date:	Fri, 2 Feb 2007 17:58:01 -0800
From:	Andrew Morton <akpm@...l.org>
To:	Nick Piggin <npiggin@...e.de>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>,
	Linux Filesystems <linux-fsdevel@...r.kernel.org>,
	Linux Memory Management <linux-mm@...ck.org>
Subject: Re: [patch 1/9] fs: libfs buffered write leak fix

On Sat, 3 Feb 2007 02:33:16 +0100
Nick Piggin <npiggin@...e.de> wrote:

> > > ===================================================================
> > > --- linux-2.6.orig/fs/buffer.c
> > > +++ linux-2.6/fs/buffer.c
> > > @@ -2344,6 +2344,8 @@ int nobh_prepare_write(struct page *page
> > >  
> > >  	if (is_mapped_to_disk)
> > >  		SetPageMappedToDisk(page);
> > > +
> > > +	/* XXX: information leak vs read(2) */
> > >  	SetPageUptodate(page);
> > >  
> > >  	/*
> > 
> > That comment is too terse to be useful.
> 
> OK, similar problem here - we have brought all the buffers uptodate
> that we are *not* going to write over, or partially write over, but
> we can have an uninitialised hole over the region we want to write.
> 
> I think just setting page uptodate in commit_write might do the
> trick? (and getting rid of the set_page_dirty there).

Yes, the page just isn't uptodate yet in prepare_write() - moving things
to commti_write() sounds sane.

But please, can we have sufficient changelogs and comments in the next version?
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