Re: [PATCH RESEND] fs: Move @f_count to different cacheline with @f_mode

[Shaokun Zhang]

Hi Aleksa,

在 2020/8/26 16:24, Aleksa Sarai 写道:
> On 2020-08-26, Shaokun Zhang <zhangshaokun@xxxxxxxxxxxxx> wrote:
>> 在 2020/8/22 0:02, Will Deacon 写道:
>>>   - This thing is tagged with __randomize_layout, so it doesn't help anybody
>>>     using that crazy plugin
>>
>> This patch isolated the @f_count with @f_mode absolutely and we don't care the
>> base address of the structure, or I may miss something what you said.
> 
> __randomize_layout randomises the order of fields in a structure on each
> kernel rebuild (to make attacks against sensitive kernel structures
> theoretically harder because the offset of a field is per-build). It is

My bad, I missed Will's comments for my poor understanding on it.

> separate to ASLR or other base-related randomisation. However it depends
> on having CONFIG_GCC_PLUGIN_RANDSTRUCT=y and I believe (at least for
> distribution kernels) this isn't a widely-used configuration.

Thanks for more explanations about it, in our test, this config is also
disabled. If having CONFIG_GCC_PLUGIN_RANDSTRUCT=y, it seems this patch
will lose its value.
If it isn't widely-used for this config, hopefully we can do something on
the scene.

Thanks,
Shaokun

>