From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@lst.de>
Subject: Re: silent semantic changes with reiser4
Date: Thu, 26 Aug 2004 14:41:19 +0200
Message-ID: <20040826124119.GA431@lst.de>
References: <20040824202521.GA26705@lst.de> <412CEE38.1080707@namesys.com> <20040825200859.GA16345@lst.de> <20040825203516.GB4688@backtop.namesys.com> <20040825205149.GA17654@lst.de> <412DA2CF.2030204@namesys.com>
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Cc: Christoph Hellwig <hch@lst.de>, Alex Zarochentsev <zam@namesys.com>,
   linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
   Alexander Lyamin aka FLX <flx@namesys.com>,
   Linus Torvalds <torvalds@osdl.org>,
   ReiserFS List <reiserfs-list@namesys.com>
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To: Hans Reiser <reiser@namesys.com>
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On Thu, Aug 26, 2004 at 01:43:59AM -0700, Hans Reiser wrote:
> >Again, O_DIRECTORY was added to solve a real-world race, not just for
> >the sake of it. 
> >
> Can you supply more details and we will try to reply concretely?  Thanks.

It's really userland programming 101 :)

 you need to fstat after open to really check that no one swtiched the
 path below you to a fifo or device, O_DIRECTORY gets that directly in
 the open call, with the additional benefit of making sure you don't
 get any of the sideeffects at all that would happen if you're opening
 a device file.

 the current reiser4 semantics break that and as soon as you're having a
 world-writeable (e.g. /tmp) dir on it and someone is doing an opendir
 on it he's lost.