[PATCH v2] drm/i915: Fix CFI violations in gt_sysfs

[Jocelyn Falempe]

On 12/01/2023 16:56, Nathan Chancellor wrote:
> Hi Jocelyn,
> 
> On Thu, Jan 12, 2023 at 11:08:17AM +0100, Jocelyn Falempe wrote:
>> This patch does also solve a kernel crash when reading
>> /sys/class/drm/card1/gt/gt0/* on a skylake machine:
>> https://bugzilla.redhat.com/show_bug.cgi?id=2154880
> 
> Interesting, I wonder what aspect of this patch fixes this because I am
> not sure that is an intended consequence of this change but that is
> still good to hear!

I wasn't able to find the root cause, but basically the kobj pointer 
given in the sysfs callback, is not the good one on this machine, so it 
either return garbage or crash.
By chance I found this patch, tried it, and it solves the issue.
> 
> For the record, this is commit a8a4f0467d70 ("drm/i915: Fix CFI
> violations in gt_sysfs") in mainline.
> 
>> Do you think it can be backported to stable releases ?
>> Conflicts are trivial on top of v6.0 at least.
> 
> I had a report from another user of this crash affecting them with kCFI
> so it is on my TODO to backport it to 6.1 (6.0 just went EOL) but I am
> currently out of the office until next Wednesday so I won't be able to
> get to it until then (as I would like to test the backport on affected
> hardware). If someone wants to beat me to it, I won't complain ;)

Thanks for taking care of it, I will wait next week then.

> 
> Cheers,
> Nathan
> 

-- 

Jocelyn