linux-kernel - Re: RFC: /dev/stdin, symlinks & permissions

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Date:	Tue, 18 Mar 2008 00:54:40 +0100
From:	Andreas Schwab <schwab@...e.de>
To:	Michael Tokarev <mjt@....msk.ru>
Cc:	Linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: RFC: /dev/stdin, symlinks & permissions

Michael Tokarev <mjt@....msk.ru> writes:

>   # ls -l /dev/pts/0
>   crw--w---- 1 root tty 136, 0 Mar 18 02:19 /dev/pts/0
>
> So far so good.  Now, I change uid to something else, --
> doing su(8) to "mjt".  /proc/self changed obviously,
> but stdin &Co is still here, and points to the same
> /dev/pts/0.  But *its* permissions/ownership did not
> change!  So now I can't, for example,
>
>  $ echo x > /dev/stdout
>  bash: /dev/stdout: Permission denied
>
> which is quite unexpected - I for one expect /dev/stdout
> to work the way very similar to /dev/tty, to mean "current
> standard output regardless of any permissions etc".

This has nothing to do with /dev/stdout.  Your terminal simply does not
allow access by anyone except user root or group tty.  You need to open
it up first, or mount /dev/pts with broader permissions (which is a bad
idea however).

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@...e.de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
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