Re: [RFC PATCH v2] mm: slub: print kernel addresses in slub debug messages

[Miles Chen]

On Thu, 2019-08-08 at 19:46 -0700, Matthew Wilcox wrote:
> On Fri, Aug 09, 2019 at 09:08:37AM +0800, miles.chen@xxxxxxxxxxxx wrote:
> > Possible approaches are:
> > 1. stop printing kernel addresses
> > 2. print with %pK,
> > 3. print with %px.
> 
> No.  The point of obscuring kernel addresses is that if the attacker manages to find a way to get the kernel to spit out some debug messages that we shouldn't
> leak all this extra information.

got it.
> 
> > 4. do nothing
> 
> 5. Find something more useful to print.

agree
> 
> > INFO: Slab 0x(____ptrval____) objects=25 used=10 fp=0x(____ptrval____)
> 
> ... you don't have any randomness on your platform?

We have randomized base on our platforms.

> But if you have randomness, at least some of these "pointers" are valuable
> because you can compare them against "pointers" printed by other parts
> of the kernel.

Understood. Keep current %p, do not leak kernel addresses.

I'll collect more cases and see if we really need some extra
information. (maybe the @offset in current message is enough)


thanks for your comments!