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Date: Mon, 23 Sep 2013 11:32:08 -0600
Subject: Re: building an online judge to evaluate Python programs
From: Modulok <modulok@gmail.com>
To: Ned Batchelder <ned@nedbatchelder.com>
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Cc: Python mailing list <python-list@python.org>, Dave Angel <davea@davea.name>
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Newsgroups: comp.lang.python
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Xref: csiph.com comp.lang.python:54654

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>
>
> If you want to run untrusted Python code and prevent malice (or stupidity)
> from harming you, you need OS-level protection.
>
>
Agreed. Just for fun here's a simple example of what could be an honest
mistake
that consumes all physical memory and swap. A well behaved kernel will kill
the
process eventually when it can no longer allocate memory, but not before
bringing the machine to its knees:

    class Foo(object):
        def __init__(self):
            self.x = 1
        def __iter__(self):
            return self
        def next(self):
            self.x += 1
            # Oops. In a well behaved iterator this should eventually
            # raise 'StopIteration'. I knew I forgot something.


    a = Foo()
    b = list(a)


-Modulok-

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<div dir=3D"ltr"><div class=3D"gmail_extra"><div class=3D"gmail_quote"><blo=
ckquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left=
-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;paddi=
ng-left:1ex">
<div bgcolor=3D"#FFFFFF" text=3D"#000000"><div><div class=3D"h5"><br></div>=
</div>
    If you want to run untrusted Python code and prevent malice (or
    stupidity) from harming you, you need OS-level protection.<span class=
=3D""><font color=3D"#888888"><br><br></font></span></div></blockquote><div=
><br></div><div>Agreed. Just for fun here&#39;s a simple example of what co=
uld be an honest mistake</div>
<div>that consumes all physical memory and swap. A well behaved kernel will=
 kill the</div><div>process eventually when it can no longer allocate memor=
y, but not before</div><div>bringing the machine to its knees:</div><div>
<br></div><div>=A0 =A0 class Foo(object):</div><div>=A0 =A0 =A0 =A0 def __i=
nit__(self):</div><div>=A0 =A0 =A0 =A0 =A0 =A0 self.x =3D 1</div><div>=A0 =
=A0 =A0 =A0 def __iter__(self):</div><div>=A0 =A0 =A0 =A0 =A0 =A0 return se=
lf</div><div>=A0 =A0 =A0 =A0 def next(self):</div><div>
=A0 =A0 =A0 =A0 =A0 =A0 self.x +=3D 1</div><div>=A0 =A0 =A0 =A0 =A0 =A0 # O=
ops. In a well behaved iterator this should eventually</div><div>=A0 =A0 =
=A0 =A0 =A0 =A0 # raise &#39;StopIteration&#39;. I knew I forgot something.=
</div><div><br></div><div><br></div>
<div>=A0 =A0 a =3D Foo()</div><div>=A0 =A0 b =3D list(a)</div><div><br></di=
v><div><br></div><div>-Modulok-</div></div></div></div>

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