[patch] rc.d/tmp (silly mkdir usage)

[Vasil Dimov]

On Tue, Aug 02, 2005 at 12:33:48PM +0300, Giorgos Keramidas wrote:
> On 2005-08-02 09:29, Vasil Dimov <vd at datamax.bg> wrote:
> > > --- /etc/rc.d/tmp.orig  Mon Aug  1 23:20:24 2005
> > > +++ /etc/rc.d/tmp       Mon Aug  1 23:22:07 2005
> > > @@ -48,8 +48,8 @@
> > >  [Nn][Oo])
> > >         ;;
> > >  *)
> > > -       if (/bin/mkdir -p /tmp/.diskless 2> /dev/null); then
> > > -               rmdir /tmp/.diskless
> > > +       if ( > /tmp/.diskless 2> /dev/null); then
> > > +               rm /tmp/.diskless
> > >         else
> > >                 if [ -h /tmp ]; then
> > >                         echo "*** /tmp is a symlink to a non-writable area!"
> >
> > The thing you suggest is bloody insecure. Just imagine some baduser
> > doing ln -s /etc/passwd /tmp/.diskless before rc.d/tmp gets executed.
> > I guess this is the reason why directory creation is used instead of
> > file creation.
> >
> > I just wonder why a new shell is forked for this test. Simply if
> > /bin/mkdir -p /tmp/.diskless 2> /dev/null ; then would do the same
> > thing without forking a new shell that only executes /bin/mkdir
> 
> I think it's because the current shell is allowed to exit if a command
> fails while a conditional test like this is run:
> 
> 	if mkdir /tmp/foo; then
> 		echo foo
> 		rmdir /tmp/foo
> 	fi
> 
> and mkdir may fail.
> 

What do you mean by "allowed to exit"?
sh -e?
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