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Date: Fri, 27 Oct 2017 21:56:19 +0200
From: "Luis R. Rodriguez" <mcgrof@kernel.org>
Subject: Re: [RFC] xfs_repair: clear file / directory attribute on symlinks
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To: "Luis R. Rodriguez" <mcgrof@kernel.org>
Cc: Nikolay Borisov <nborisov@suse.com>, "Darrick J. Wong" <darrick.wong@oracle.com>, Eric Sandeen <sandeen@sandeen.net>, linux-xfs@vger.kernel.org, Laurent Bonnaud <Laurent.Bonnaud@inpg.fr>, Tso Ted <tytso@mit.edu>, Flex Liu <fliu@suse.com>, Jake Norris <jake.norris@suse.com>, Jan Kara <jack@suse.cz>

On Fri, Oct 27, 2017 at 07:03:39PM +0200, Luis R. Rodriguez wrote:
> > > 	file = argv[2];
> > > 
> > > 	fd = open(file, open_flags);
> > > 	if (!fd) {
> > > 		printf("Could not open file for operation: %s\n", cmd_str);
> > > 		usage();
> > > 	}
> 
> This open() will though.

That's because the special mushrooms I took the day I wrote the above
code made me forget to instead check for:

	if (fd < 0)

That will always fail.

So open() on a dangling symlink will fail as well.

So it seems we can't set these attributes via userspace, unless you
use xfs_db and as noted by Darrick that's not a valid use case, it'd
be fuzzing.

  Luis