[Intel-gfx] [PATCH 1/1] drm/i915: shorten i915_next_seqno debugfs output

[Kees Cook]

On Fri, Apr 12, 2013 at 2:15 AM, Mika Kuoppala
<mika.kuoppala at linux.intel.com> wrote:
> Kees Cook <keescook at chromium.org> writes:
>
>> On Thu, Apr 11, 2013 at 9:15 AM, Mika Kuoppala
>> <mika.kuoppala at linux.intel.com> wrote:
>>> Kees Cook <keescook at chromium.org> writes:
>>>
>>>> On Thu, Apr 11, 2013 at 6:22 AM, Mika Kuoppala
>>>> <mika.kuoppala at linux.intel.com> wrote:
>>>>> commit 647416f9eefe7699754b01b9fc82758fde83248c
>>>>> Author: Kees Cook <keescook at chromium.org>
>>>>> Date:   Sun Mar 10 14:10:06 2013 -0700
>>>>>
>>>>>     drm/i915: use simple attribute in debugfs routines
>>>>>
>>>>> made i915_next_seqno debugfs entry to crop it's output
>>>>> if returned value was large enough. Using simple_attr
>>>>> will limit the output to 24 bytes. Fix this by returning
>>>>> only the value and nothing else.
>>>>>
>>>>> Cc: Kees Cook <keescook at chromium.org>
>>>>> Signed-off-by: Mika Kuoppala <mika.kuoppala at intel.com>
>>>>
>>>> Oh! Thanks for catching that. What a weird limitation.
>>>>
>>>> What about max freq, min freq, and wedged? Do those run the risk of
>>>> truncation too?
>>>
>>> max and min freq should be safe, and wedged too on 32bit platforms.
>>> But if gpu is declared wedged on host with 64bit atomic_t,
>>> it will crop the output.
>>
>> Should we consider proposing an increase in the size of the simple
>> attr buffer? It seems silly to provide an arbitrary format string but
>> leave the buffer so small.
>
> That or dynamic allocation to attr->get_buf. But that would need
> extra pass with snprintf and I don't know if that qualifies as 'simple'
> anymore.
>
> I have posted a patch which fixes all i915 debugfs simple attributes
> to fit into the simple_attr by removing everything except the fmt to
> value. I didn't find any testcases which would rely on preample
> being there.

That works too. :) If you want, consider them:

Acked-by: Kees Cook <keescook at chromium.org>

:)

Thanks!

-Kees

--
Kees Cook
Chrome OS Security