Messages in this thread | | | Subject | Re: thoughts on kernel security issues | Date | Fri, 14 Jan 2005 09:39:36 -0300 | From | Horst von Brand <> |
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Linus Torvalds <torvalds@osdl.org> said: > On Thu, 13 Jan 2005, Alan Cox wrote: > > On Iau, 2005-01-13 at 16:38, Linus Torvalds wrote:
> > > It wouldn't be a global flag. It's a per-process flag. For example, > > > many people _do_ need to execute binaries in their home directory. I > > > do it all the time. I know what a compiler is.
> > noexec has never been worth anything because of scripts. Kernel won't > > load that binary, I can write a script to do it.
> Scripts can only do what the interpreter does. And it's often a lot harder > to get the interpreter to do certain things. For example, you simply > _cannot_ get any thread race conditions with most scripts out there, nor > can you generally use magic mmap patterns.
But you can trivially run an executable via e.g.:
/lib/ld-2.3.4.so some-nice-proggie
and the execute permissions (and noexec, etc) on some-nice-proggie don't matter.
> Am I claiming that disallowing self-written ELF binaries gets rid of all > security holes? Obviously not.
It makes their running a bit harder, but not much.
> I'm claiming that there are things that > people can do that make it harder, and that _real_ security is not about > trusting one subsystem, but in making it hard enough in many independent > ways that it's just too effort-intensive to attack.
Right. But this is a broken idea, IMVHO.
Besides, something that has been overlooked in all this discussion so far: It does routinely happen that fixing some "just an ordinary bug" really does correct a security problem. Plus backporting "only security fixes" gets harder and harder as they start depending on other random changes. -- Dr. Horst H. von Brand User #22616 counter.li.org Departamento de Informatica Fono: +56 32 654431 Universidad Tecnica Federico Santa Maria +56 32 654239 Casilla 110-V, Valparaiso, Chile Fax: +56 32 797513 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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