linux-kernel - Re: [RFC PATCH 8/9] orangefs: use set/clear_fs_page

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Message-ID: <20200427022709.GC2005@dread.disaster.area>
Date:   Mon, 27 Apr 2020 12:27:09 +1000
From:   Dave Chinner <david@...morbit.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Guoqing Jiang <guoqing.jiang@...ud.ionos.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        hch@...radead.org, Mike Marshall <hubcap@...ibond.com>,
        Martin Brandenburg <martin@...ibond.com>,
        devel@...ts.orangefs.org
Subject: Re: [RFC PATCH 8/9] orangefs: use set/clear_fs_page_private

On Sun, Apr 26, 2020 at 05:12:34PM -0700, Matthew Wilcox wrote:
> On Mon, Apr 27, 2020 at 08:24:55AM +1000, Dave Chinner wrote:
> > > @@ -460,17 +456,13 @@ static void orangefs_invalidatepage(struct page *page,
> > >  
> > >  	if (offset == 0 && length == PAGE_SIZE) {
> > >  		kfree((struct orangefs_write_range *)page_private(page));
> > > -		set_page_private(page, 0);
> > > -		ClearPagePrivate(page);
> > > -		put_page(page);
> > > +		clear_fs_page_private(page);
> > 
> > Ditto:
> > 		wr = clear_fs_page_private(page);
> > 		kfree(wr);
> 
> You don't want to be as succinct as the btrfs change you suggested?
> 
> 		kfree(clear_fs_page_private(page));

That could be done, yes. I was really just trying to point out the
use after free that was occurring here rather than write compact
code...

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com