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Date:   Mon, 7 Dec 2020 22:49:03 +0000
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     "Eric W. Biederman" <ebiederm@xmission.com>
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Subject: Re: [PATCH v2 09/24] file: Replace fcheck_files with
 files_lookup_fd_rcu
Message-ID: <20201207224903.GA4117703@ZenIV.linux.org.uk>
References: <87r1on1v62.fsf@x220.int.ebiederm.org>
 <20201120231441.29911-9-ebiederm@xmission.com>
 <20201207224656.GC4115853@ZenIV.linux.org.uk>
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On Mon, Dec 07, 2020 at 10:46:57PM +0000, Al Viro wrote:
> On Fri, Nov 20, 2020 at 05:14:26PM -0600, Eric W. Biederman wrote:
> 
> >  /*
> >   * Check whether the specified fd has an open file.
> >   */
> > -#define fcheck(fd)	fcheck_files(current->files, fd)
> > +#define fcheck(fd)	files_lookup_fd_rcu(current->files, fd)
> 
> Huh?
> fs/file.c:1113: file = fcheck(oldfd);
> 	dup3(), under ->file_lock, no rcu_read_lock() in sight
> 
> fs/locks.c:2548:                f = fcheck(fd);
> 	fcntl_setlk(), ditto
> 
> fs/locks.c:2679:                f = fcheck(fd);
> 	fcntl_setlk64(), ditto
> 
> fs/notify/dnotify/dnotify.c:330:        f = fcheck(fd);
> 	fcntl_dirnotify(); this one _is_ under rcu_read_lock().
> 
> 
> IOW, unless I've missed something earlier in the series, this is wrong.

I have missed something, all right.  Ignore that comment...