Re: [patch 0/5] Support for sanitization flag in low-level page allocator

Peter Zijlstra
2009-05-30T13:24:20Z

On Sat, 2009-05-30 at 15:21 +0200, Peter Zijlstra wrote:
> On Sat, 2009-05-30 at 13:42 +0200, pageexec@freemail.hu wrote:
> > > Why waste time on this?
> >
> > e.g., when userland executes a syscall, it 'can run kernel code'. if that kernel
> > code (note: already exists, isn't provided by the attacker) gives unintended
> > kernel memory back to userland, there is a problem. that problem is addressed
> > in part by early sanitizing of freed data.
>
> Right, so the whole point is to minimize the impact of actual bugs,
> right? So why not focus on fixing those actual bugs? Can we create tools
> to help us find such bugs faster? We use sparse for a lot of static
> checking, we create things like lockdep and kmemcheck to dynamically
> find trouble.
>
> Can we instead of working around a problem, fix the actual problem?

Also, I'm not at all opposed to make crypto code use kzfree(). That code
knows it had sensitive data in memory, it can wipe the memory when it
frees it -- that makes perfect sense.

Wiping everything because we're too 'lazy' to figure out what really
matters otoh seems silly.