linux-kernel - Re: [RFC] a corner case of open(2)

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Message-ID: <89187.1461696097@turing-police.cc.vt.edu>
Date:	Tue, 26 Apr 2016 14:41:37 -0400
From:	Valdis.Kletnieks@...edu
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC] a corner case of open(2)

On Tue, 26 Apr 2016 18:55:38 +0100, Al Viro said:

> 	It is a change of user-visible behaviour, but I would be very
> surprised if anything broke from that change.  And it would help to simplify
> the awful mess we have in there.

I have to admit that over the past 3 decades of working with Unix-y systems,
there's been a number of times I've had to resort to 'od -cx /your/dir/here'
to debug issues (/bin/ls -fi is *almost* equivalent, but doesn't show holes
in the directory)

The biggest danger I can see is some shell script doing something like:

foobar > $dir/$targetfile

and $targetfile is unset. If we allow a program to get an open fd that refers
to a directory, what are the semantics of various operations on that fd?


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