1. Is Euphoria a virus ?
As a result of somebody running a rather questionable CGI script that I
wrote in Eu, my College student server was totally dead for 18 hours. It
unfortunately happens that this server handles just about everything
student in the college - everybody's web sites, including countless
societies, student email, the student linux system, student filespace and
the system for common username-password access to multiple machines. All
of these facilities were unavailable during this time.
So what, you might say. Well the script I wrote was a simple test to see
how many dimensions I could get in a sequence before memory ran
out. Million-dimensional sequences were no problem, bravo ! But
unfortunately when given too much to do, and running out of memory, this
programme has an awful tendency to take other tasks down with it
(presumably because it takes the memory that they were just about to
grab). When this task happens to be inetd and the said machine is locked
away somewhere you have a problem ie dead computer.
There is an inherent flaw somewhere, perhaps in the ethos of the linux
kernel, or perhaps in eu's attitude to memory. The local nerds are
convinced that I am unreasonable, and that eu is inherently evil.
I wonder whether C, for example, could potentially cause the same
problem. What bugs me is that any undebugged programme that uses recursion
could cause this same problem, and I don't want to get eaten alive again
for crashing the student server.
What needs to change ? Eu or Linux ?
Daniel
--
Today's Proverb :
Trust in the Lord with all your heart, do not rely on your own understanding
(3v5)
Daniel Johnson Engineer, smartypants and clown
Jesus College, Cambridge all at a very reasonable price
dpj22 at cam.ac.uk
zeus.jesus.cam.ac.uk/~dpj22 talk dpj22 at jewish.jesus.cam.ac.uk
2. Re: Is Euphoria a virus ?
On Sun, 12 Mar 2000, Daniel wrote:
> As a result of somebody running a rather questionable CGI script that I
> wrote in Eu, my College student server was totally dead for 18 hours. It
> unfortunately happens that this server handles just about everything
> student in the college - everybody's web sites, including countless
> societies, student email, the student linux system, student filespace and
> the system for common username-password access to multiple machines. All
> of these facilities were unavailable during this time.
>
> So what, you might say. Well the script I wrote was a simple test to see
> how many dimensions I could get in a sequence before memory ran
> out. Million-dimensional sequences were no problem, bravo ! But
> unfortunately when given too much to do, and running out of memory, this
> programme has an awful tendency to take other tasks down with it
> (presumably because it takes the memory that they were just about to
> grab). When this task happens to be inetd and the said machine is locked
> away somewhere you have a problem ie dead computer.
Daniel:
I tried duplicating the problem, but all I got was a slight slowing of
xWindows, and eventually, Euphoria exited with an out-of-memory
message and ex.err file when the sequence grew to 20megs. (Understandable,
I only have 28megs on the computer). Everything else continues to run normally.
If you will send the cgi program in question via private e-mail, I will try
again with that.
Regards,
Irv
3. Re: Is Euphoria a virus ?
>I tried duplicating the problem, but all I got was a slight slowing of
>xWindows, and eventually, Euphoria exited with an out-of-memory
>message and ex.err file when the sequence grew to 20megs. (Understandable,
>I only have 28megs on the computer). Everything else continues to run normally.
Certain machines seemed vulnerable to it, while others showed no side
effects. It was probably run 50 times on the webserver with no known side
effects prior to the fatal incident. All it did was recursively put
sequences inside each other. On most machines it just ran out of memory
and quit.
>If you will send the cgi program in question via private e-mail, I will try
>again with that.
Well I guess if you destroy a virus you reduce the chances of finding a
cure, but I zapped it anyway.
Daniel
--
Today's Proverb :
Trust in the Lord with all your heart, do not rely on your own understanding
(3v5)
Daniel Johnson Engineer, smartypants and clown
Jesus College, Cambridge all at a very reasonable price
dpj22 at cam.ac.uk
zeus.jesus.cam.ac.uk/~dpj22 talk dpj22 at jewish.jesus.cam.ac.uk
4. Re: Is Euphoria a virus ?
Daniel Johnson writes:
> The local nerds are convinced that I am unreasonable,
> and that eu is inherently evil.
> I wonder whether C, for example, could potentially
> cause the same problem.
I'd like to be able to claim that Euphoria has magical
properties that allow it to do things that can't be done
by C, but the fact is that Euphoria is calling standard
C library routines (malloc and free) which are making
standard Linux system calls. The same series of
calls could be done in C.
It sounds like Linux gave so much memory to your
process that some important kernel process got blocked,
and a kind of "deadlock" occurred.
Regards,
Rob Craig
Rapid Deployment Software
http://www.RapidEuphoria.com
5. Re: Is Euphoria a virus ?
Daniel Johnson wrote:
>
> As a result of somebody running a rather questionable CGI script that I
> wrote in Eu, my College student server was totally dead for 18 hours. It
> unfortunately happens that this server handles just about everything
> student in the college - everybody's web sites, including countless
> ----SNIP----
---------------------------------
It is always the responsibility of the operating system to
protect applications from each other.
If this doesn't happen, then applications (in any language)
will frequently destroy each other and the operating system
itself.
6. Re: Is Euphoria a virus ?
Daniel Johnson wrote:
>There is an inherent flaw somewhere, perhaps in the ethos of the linux
>kernel, or perhaps in eu's attitude to memory. The local nerds are
>convinced that I am unreasonable, and that eu is inherently evil.
>
>I wonder whether C, for example, could potentially cause the same
>problem. What bugs me is that any undebugged programme that uses recursion
>could cause this same problem, and I don't want to get eaten alive again
>for crashing the student server.
>
>What needs to change ? Eu or Linux ?
>
What needs to change is your willingness to saw on the branch that you
are standing on, especially if you have company. It was fairly predictable
that the test you were running would bring the machine to it's knees even
if it did not crash it. The admins should have put some limits on the
resources you were allowed to consume, but then a little common sense
on your part would not have hurt either. Next time you want to stress test
somebody else's machine, why not warn the admins and request some
standalone time. It is fairly understandable that they don't want you
playing any more fun and games. It is too bad that Eu gets besmirched
along with you. Try apologizing, showing them your code and doing a
bit of fence mending.
Everett L.(Rett) Williams
rett at gvtc.com
7. Re: Is Euphoria a virus ?
On Sun, 12 Mar 2000, you wrote:
> Daniel Johnson wrote:
...
> >
> >What needs to change ? Eu or Linux ?
> >
> What needs to change is your willingness to saw on the branch that you
> are standing on, especially if you have company. It was fairly predictable
> that the test you were running would bring the machine to it's knees even
> if it did not crash it. The admins should have put some limits on the
> resources you were allowed to consume, but then a little common sense
> on your part would not have hurt either. Next time you want to stress test
> somebody else's machine, why not warn the admins and request some
> standalone time. It is fairly understandable that they don't want you
> playing any more fun and games. It is too bad that Eu gets besmirched
> along with you. Try apologizing, showing them your code and doing a
> bit of fence mending.
The consensus of opinion on my Linux maillist was:
while it is not at all likely that you could actually crash a Linux server this
way (the worst that should happen is a segfault in your program),
it is entirely possible that the program could have eaten up 99%+ of the
processor's time. That would have pretty much the same result as a crash,
unless someone was there to re-nice or kill your runaway program.
Perhaps the sysadmin should take a look at putting some quotas on things.
Regards,
Irv
8. Re: Is Euphoria a virus ?
> > >What needs to change ? Eu or Linux ?
> The consensus of opinion on my Linux maillist was:
> while it is not at all likely that you could actually crash a Linux server
> this
> way (the worst that should happen is a segfault in your program),
> it is entirely possible that the program could have eaten up 99%+ of the
> processor's time. That would have pretty much the same result as a crash,
> unless someone was there to re-nice or kill your runaway program.
> Perhaps the sysadmin should take a look at putting some quotas on things.
> -Irv
Then tell me, could the same effect be achieved by an endless while loop ?
If so then I can use neither recursion nor while loops in CGI scripts out
of fear that a random bug would cause it to crash when somebody tried it
in the middle of the night.
This would be somewhat restrictive, which would defeat the object of using
Euphoria in the first place.
Daniel
--
Today's Proverb :
He who walks purely walks securely, but he who walks in crooked ways will be
found out (10v9)
Daniel Johnson Engineer, smartypants and clown
Jesus College, Cambridge all at a very reasonable price
dpj22 at cam.ac.uk
zeus.jesus.cam.ac.uk/~dpj22 talk dpj22 at jewish.jesus.cam.ac.uk
9. Re: Is Euphoria a virus ?
On Tue, 14 Mar 2000, you wrote:
> > > >What needs to change ? Eu or Linux ?
> > The consensus of opinion on my Linux maillist was:
> > while it is not at all likely that you could actually crash a Linux server
> > this
> > way (the worst that should happen is a segfault in your program),
> > it is entirely possible that the program could have eaten up 99%+ of the
> > processor's time. That would have pretty much the same result as a crash,
> > unless someone was there to re-nice or kill your runaway program.
> > Perhaps the sysadmin should take a look at putting some quotas on things.
> > -Irv
>
> Then tell me, could the same effect be achieved by an endless while loop ?
Of course. The loop would be more effective if written in C, however.
Euphoria isn't fast enough to use up _all_ the CPU cycles.
> If so then I can use neither recursion nor while loops in CGI scripts out
> of fear that a random bug would cause it to crash when somebody tried it
> in the middle of the night.
> This would be somewhat restrictive, which would defeat the object of using
> Euphoria in the first place.
This has nothing to do with recursion, loops, or choice of language.
Ask your sysadmins to look up ulimit in their bash manual. It allows limits
to be set on how much of a system's reources can be allocated to a particular
process.
Obviously, if the machine is doing other important things, they shouldn't allow
any one user or program to commandeer _all_ available resources.
Regards,
Irv
