Re: [RFC][PATCH] x86: Verify access_ok() context

[David Smith]

On 01/18/2017 06:19 PM, Andy Lutomirski wrote:
> On Wed, Jan 18, 2017 at 2:16 PM, David Smith <dsmith@xxxxxxxxxx> wrote:
>> On 01/16/2017 03:14 PM, Thomas Gleixner wrote:
>>> On Mon, 16 Jan 2017, David Smith wrote:

... stuff deleted ...

>>>> If you put that new access_ok() call in a module that gets
>>>> loaded/unloaded, you see one warning for every module load, which gets a
>>>> bit annoying.
>>>
>>> Can you please elaborate where this access_ok() is placed in the module
>>> code?
>>
>> It doesn't really matter where you place the access_ok() call in the module
>> code. If you call access_ok() in a module, then that module has its own
>> WARN_ON_ONCE() static variable. If access_ok() was a function exported
>> from the kernel, then there would be only one copy of the WARN_ON_ONCE()
>> static variable.
> 
> That doesn't seem like such a big deal to me.

To be clear here, I'm not suggesting we replace the access_ok() macro
with an exported kernel function. I'm just stating the fact that if you
have several modules that call the access_ok() macro (or one module that
gets loaded/unloaded/reloaded multiple times), each one can produce the
new warning. I'm not seeing a "flood" of these new warnings, but a
steady enough stream of them to be annoying.

-- 
David Smith
dsmith@xxxxxxxxxx
Red Hat
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