Re: [v3] mm: Add SLUB free list pointer obfuscation

[Alexander Popov]

Hello Christopher and Kees,

Excuse me for the delayed reply.

On 28.07.2017 02:53, Christopher Lameter wrote:
> On Fri, 28 Jul 2017, Alexander Popov wrote:
> 
>> I don't really like ignoring double-free. I think, that:
>>   - it will hide dangerous bugs in the kernel,
>>   - it can make some kernel exploits more stable.
>> I would rather add BUG_ON to set_freepointer() behind SLAB_FREELIST_HARDENED. Is
>> it fine?
> 
> I think Kees already added some logging output.

Hm, I don't see anything like that in v4 of "SLUB free list pointer
obfuscation": https://patchwork.kernel.org/patch/9864165/

>> At the same time avoiding the consequences of some double-free errors is better
>> than not doing that. It may be considered as kernel "self-healing", I don't
>> know. I can prepare a second patch for do_slab_free(), as you described. Would
>> you like it?
> 
> The SLUB allocator is already self healing if you enable the option to do
> so on bootup (covers more than just the double free case). What you
> propose here is no different than that and just another way of having
> similar functionality. In the best case it would work the same way.

Ok, I see. Thanks.

Best regards,
Alexander