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Date: Tue, 2 Aug 2005 14:38:36 +0300
From: Giorgos Keramidas <keramida@linux.gr>
To: Vasil Dimov <vd@datamax.bg>
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Cc: freebsd-hackers@freebsd.org
Subject: Re: [patch] rc.d/tmp (silly mkdir usage)
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On 2005-08-02 14:05, Vasil Dimov <vd@datamax.bg> wrote:
>On Tue, Aug 02, 2005 at 12:33:48PM +0300, Giorgos Keramidas wrote:
>>On 2005-08-02 09:29, Vasil Dimov <vd@datamax.bg> wrote:
>>>>  *)
>>>> -       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?

You're right, of course.  I forgot the script I was looking at had the -e
option enabled.