Re: [PATCH 10/10] powerpc: remove address space overrides using set_fs()

Christophe Leroy
2020-09-02T14:07:36Z

Le 02/09/2020 à 15:13, David Laight a écrit :
> From: Christoph Hellwig
>> Sent: 02 September 2020 13:37
>>
>> On Wed, Sep 02, 2020 at 08:15:12AM +0200, Christophe Leroy wrote:
>>>> - return 0;
>>>> - return (size == 0 || size - 1 <= seg.seg - addr);
>>>> + if (addr >= TASK_SIZE_MAX)
>>>> + return false;
>>>> + if (size == 0)
>>>> + return false;
>>>
>>> __access_ok() was returning true when size == 0 up to now. Any reason to
>>> return false now ?
>>
>> No, this is accidental and broken. Can you re-run your benchmark with
>> this fixed?
>
> Is TASK_SIZE_MASK defined such that you can do:
>
> return (addr | size) < TASK_SIZE_MAX) || !size;

TASK_SIZE_MAX will usually be 0xc0000000

With:
addr = 0x80000000;
size = 0x80000000;

I expect it to fail ....

With the formula you propose it will succeed, won't it ?

Christophe