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Message-ID: <2cd57c900511302125g9e771c6w@mail.gmail.com>
Date: Thu, 1 Dec 2005 13:25:50 +0800
From: Coywolf Qi Hunt <coywolf@gmail.com>
To: "Tomar, Nagendra" <nagendra_tomar@adaptec.com>
Subject: Re: Why does insmod _not_ check for symbol redefinition ??
Cc: Rusty Russell <rusty@rustcorp.com.au>, linux-kernel@vger.kernel.org
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2005/12/1, Nagendra Singh Tomar <nagendra_tomar@adaptec.com>:
> On Thu, 1 Dec 2005, Rusty Russell wrote:
>
> > Sure.  It was due to minimalism.  If you override a symbol it's
> > undefined behavior.  It should be fairly simple to add a check that
> > noone overrides a symbol.  We didn't bother checking for it because it
> > wasn't clear that it was problematic.
>
> Thanx.
> Of all the problems (including kernel crashes, BUGs etc) one of the
> more serious  kinds are the ones where someone writes a new module and
> accidently  defines a function which has the same name as one of functions
> (say  foo_export),  already EXPORTed by either kernel proper or some
> loaded  module (as the  kernel is growing bigger chances of this happening
> is also  growing). The module happily loads and then some other module
> which wants  to use the function foo_export (obviously the one EXPORTed by
> kernel  proper and not the one overidden by the overiding module) is
> loaded. It  will also load happily but will get linked against the new
> foo_export,  defnitely not something that he wants. And, all this has
> happened without the kernel telling the user anything.
>         IMHO, these kind of silent errors are very dangerous and not
> something that should be acceptable.
> As you rightly said, it should be fairly straightforward to check for
> symbol redefinition. We need to do it only for the symbols EXPORTed by the
> loadable module.

This shouldn't happen if you only use in-tree modules as you should.
Don't take kernel modules as user mode applications.
--
Coywolf Qi Hunt
http://sosdg.org/~coywolf/
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