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Date: Mon, 23 Nov 2009 16:16:13 +0300
From: Anton Vorontsov <avorontsov@ru.mvista.com>
To: David Woodhouse <dwmw2@infradead.org>
Subject: Re: [PATCH] jffs2: Fix memory corruption in jffs2_read_inode_range()
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On Sun, Nov 22, 2009 at 10:20:59AM +0000, David Woodhouse wrote:
> On Fri, 2009-11-20 at 12:45 -0700, Anton Vorontsov wrote:
> > +       if (pg->index > ((i_size_read(inode) - 1) >> PAGE_CACHE_SHIFT)) {
> > +               ret = 0;
> > +               memset(pg_buf, 0, PAGE_CACHE_SIZE);
> > +       } else {
> > +               ret = jffs2_read_inode_range(c, f, pg_buf,
> > +                       pg->index << PAGE_CACHE_SHIFT, PAGE_CACHE_SIZE);
> > +       } 
> 
> Thank you for the excellent diagnosis and the patch. 
> 
> I think I'd prefer to fix it a little differently though -- I would be
> happier to make jffs2_read_inode_range() cope with out-of-file reads,
> rather than adding this special case where we don't call it.
> 
> That way we aren't at all susceptible to potential races between the
> VFS-maintained i_size and our own internal fragtree handling. And
> jffs2_read_inode_range() already handles the memset to zero for various
> other reasons anyway.
> 
> Does this patch look OK to you? It seems to work on the test cases I've
> tried.

Yep, it looks good (and works).

Thanks David!

-- 
Anton Vorontsov
email: cbouatmailru@gmail.com
irc://irc.freenode.net/bd2