GNU bug report logs - #10363
/etc/mtab -> /proc/mounts symlink affects df(1) output for /

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Message #65 received at 10363 <at> debbugs.gnu.org (full text, mbox):

From: Henrique de Moraes Holschuh <hmh <at> debian.org>
To: Goswin von Brederlow <goswin-v-b <at> web.de>
Cc: Paul Eggert <eggert <at> cs.ucla.edu>, Alan Curry <pacman-cu <at> kosh.dhis.org>,
	653073 <at> bugs.debian.org, debian-devel <at> lists.debian.org,
	10363 <at> debbugs.gnu.org, jidanni <at> jidanni.org, rleigh <at> codelibre.net
Subject: Re: bug#10363: /etc/mtab -> /proc/mounts symlink affects df(1)
	output for
Date: Thu, 19 Jan 2012 09:23:00 -0200

On Thu, 19 Jan 2012, Goswin von Brederlow wrote:
> Paul Eggert <eggert <at> cs.ucla.edu> writes:
> > On 01/18/12 06:25, Goswin von Brederlow wrote:
> >> What df should do is automatically skip the entries that are obscured or
> >> generally inaccessible.
> >
> > Isn't this missing some of the larger context?  df is just doing what
> > lots of other programs do: finding out what file systems one has,
> > and reporting statistics on them.  It sounds suboptimal to require
> > the maintainers of all these programs (coreutils, nautilus, etc.)
> > to rewrite their apps to deal with obscured entries.  Surely it would
> > be better to have the kernel ordinarily return just the ordinary entries,
> > and to return obscured entries only when they are specially requested.
> > That way, this issue would be isolated to the few bits of code that really
> > want to see obscured entries.
> 
> +1. Kernel knows best anyway.

The kernel has to return all entries that are visible to the current
namespace, otherwise you pretty much cannot know about the existence of
shadowed entries in the first place, and that has all sort of nasty
implications for security and troubleshooting.

The kernel should NOT include entries that are out of reach due to
namespaces or chrooting, but I don't think this is quite correct right now.

If you don't want to show to the user shadowed entries, fix it in the
UI, maybe write a nice LGPL lib and get the various GNU utils to use it
to avoid duplicated effort...  or fix it in glibc, if applicable.  But
/proc/mounts really has to return complete information.

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh

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