[Cfengine-develop] Kind of a bug, maybe

[Luke A. Kanies]

Hi Mark,

I kind of found a bug in cfengine today.  Well, I know I found one and I 
kind of found another.

First, the known bug:

Cfengine should probably never move a file that already ends in '.cfsaved' 
to <filename>.cfsaved.  I've had multiple occasions where I've had files 
named something like file.cfsaved.cfsaved.cfsaved, and it can be quite 
disastrous sometimes.  If you don't know of a simple way to fix this, I 
can probably provide a patch.

Now to the kind-of bug:

Run the following shell script:

#!/bin/sh

bd=/tmp/cftest
mkdir $bd

mkdir -p $bd/orig/a
touch $bd/orig/a/b
mkdir $bd/new
ln -s $bd/orig/a $bd/new

--------------------------------
You now have a simple directory structure in /tmp.  Now run the following 
simple cfengine script (I highly recommend -v):

control:
    actionsequence = ( links )
    bd = ( /tmp/cftest )

links:
    ${bd}/new +>! ${bd}/orig r=inf

-----------------------------------

You now have a very destroyed directory.  This error is the first clue:

cfengine:: Moving /tmp/cftest/new/a/b to /tmp/cftest/new/a/b.cfsaved
cfengine:: INFO: /tmp/cftest/new/a is a symbolic link, not a true 
directory!
cfengine:: Linking files /tmp/cftest/new/a/b -> /tmp/cftest/orig/a/b

> From there, you get a lot of badness.  The whole problem is because of the 
link done in the shell script, cfengine is actually linking from a file 
directly back to itself, just with a different filename, because 
/tmp/cftest/orig/a/b is the exact same file as /tmp/cftest/new/a/b.

I call this "kind of a bug" because I don't know the best solution.  My 
initial reaction is that cfengine should get rid of the soft link, create 
a directory, and go on its merry way.  That quite possibly is a very bad 
thing, though.

It seems like the best response is just make sure that a file is never 
linked to itself; if the file you're linking to exists then stat it to 
make sure it is not the same file.

And, of course, this is a very handy demonstration of the chaos that 
results from saving files that have already been saved via cfengine:

cfengine:: Can't rename 
/tmp/cftest/new/a/b_1093061372_Fri_Aug_20_23_09_32_2004_.cfsaved_1093061372_Fri_Aug_20_23_09_32_2004_.cfsaved_1093061372_Fri_Aug_20_23_09_32_2004_.cfsaved_1093061372_Fri_Aug_20_23_09_32_2004_.cfsaved_1093061372_Fri_Aug_20_23_09_32_2004_.cfsaved 
to 
/tmp/cftest/new/a/b_1093061372_Fri_Aug_20_23_09_32_2004_.cfsaved_1093061372_Fri_Aug_20_23_09_32_2004_.cfsaved_1093061372_Fri_Aug_20_23_09_32_2004_.cfsaved_1093061372_Fri_Aug_20_23_09_32_2004_.cfsaved_1093061372_Fri_Aug_20_23_09_32_2004_.cfsaved_1093061372_Fri_Aug_20_23_09_32_2004_.cfsaved
cfengine:: rename: File name too long

I don't really know what the resolution is, but someone needs to be done; 
this quite destroyed my (fortunately small) network, and if I had shipped 
this file off to my clients before this happened to me... I shudder quite 
a bit.

What do you think?

Luke

--
Nature and nature's laws lay hid in night,
God said, "Let Newton be," and all was light.

It did not last; the devil howling "Ho!
Let Einstein be!" restored the status quo.
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Luke Kanies | http://abstractive.org | http://reductiveconsulting.com