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Date: Thu, 27 Sep 2007 01:53:06 +1000 (EST)
From: Ian Smith <smithi@nimnet.asn.au>
To: LI Xin <d@delphij.net>
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Cc: freebsd-stable@freebsd.org
Subject: Re: rm(1) bug, possibly serious
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On Tue, 25 Sep 2007, LI Xin wrote:
 > Oliver Fromme wrote:
 > > Nicolas Rachinsky wrote:
 > >  > Oliver Fromme wrote:
 > >  > > By the way, an additional confusion is that ".." and "../"
 > >  > > are handled differently.  Specifying ".." always leads to
 > >  > > this message:
 > >  > > 
 > >  > > rm: "." and ".." may not be removed
 > >  > > 
 > >  > > and nothing is actually removed.  It is confusing that
 > >  > > adding a slash leads to a different error message _and_
 > >  > > removal of the contents of the parent directory.  Clearly
 > >  > > a POLA violation.

Clearly a bug, and well spotted, especially if as old as reported.

 > >  > 
 > >  > Adding a slash often leads to different behaviour.
 > > 
 > > Yes, I'm aware of that.  I often make use of the feature
 > > that "find /sys/" expands the symlink, while "find /sys"
 > > does not.  The same holds true for ls(1).

But fortunately not for rm(1):

     The rm utility removes symbolic links, not the files referenced by the
     links.

     It is an error to attempt to remove the files /, . or ..

 > > However, I would still argue that there is no sane reason
 > > for "rm -rf ../" behaving differently from "rm -rf ..",
 > > especially because it behaves differently in a destructive
 > > way.  That's why I call it a POLA violation.
 > 
 > Also a POSIX violation IMHO :-)

Indeed; I can't imagine a situation where removing "." (let alone "..") 
and so orphaning the pwd might be considered sane, never mind legal .. 
but maybe I lack imagination :) 

Cheers, Ian