[patch] rc.d/tmp (silly mkdir usage)
Giorgos Keramidas
keramida at linux.gr
Tue Aug 2 11:38:52 GMT 2005
On 2005-08-02 14:05, Vasil Dimov <vd at 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 at 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.
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