Messages in this thread | | | Date | Thu, 13 Jan 2005 09:33:38 -0800 (PST) | From | Linus Torvalds <> | Subject | Re: thoughts on kernel security issues |
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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.
Am I claiming that disallowing self-written ELF binaries gets rid of all security holes? Obviously not. 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.
It's the same thing with passwords. Clearly any password protected system can be broken into: you just have to guess the password. It then becomes a matter of how hard it is to "guess" - at some point you say a password is secure not because it is a password, but because it's too _expensive_ to guess/break.
So all security issues are about balancing cost vs gain. I'm convinced that the gain from openness is higher than the cost. Others will disagree.
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