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Subject: Re: [PATCH] drm/i915/gvt/scheduler: fix potential NULL pointer
 dereference
To: Chris Wilson <chris@chris-wilson.co.uk>,
        Zhenyu Wang <zhenyuw@linux.intel.com>, Zhi Wang <zhi.a.wang@intel.com>,
        Jani Nikula <jani.nikula@linux.intel.com>,
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From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
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Date: Mon, 19 Mar 2018 16:45:24 -0500
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On 03/19/2018 04:23 PM, Chris Wilson wrote:
> Quoting Gustavo A. R. Silva (2018-03-19 20:50:12)
>> Hi Chris,
>>
>> On 03/19/2018 03:38 PM, Chris Wilson wrote:
>>> Quoting Gustavo A. R. Silva (2018-03-19 19:30:53)
>>>> _workload_ is being dereferenced before it is null checked, hence
>>>> there is a potential null pointer dereference.
>>>>
>>>> Fix this by moving the pointer dereference after _workload_ has
>>>> been null checked.
>>>
>>> The checks are misleading and not required.
>>
>> All of them?
>>
>> if (!workload || !reg_state || workload->ring_id != RCS)
>>          return;
> 
> workload can not be NULL (dereference in caller), reg_state can not be
> NULL (by construct from kmap()).
> 
> It may be not an RCS ring through

I got it.

I'll send the following patch then:

--- a/drivers/gpu/drm/i915/gvt/scheduler.c
+++ b/drivers/gpu/drm/i915/gvt/scheduler.c
@@ -74,7 +74,7 @@ static void sr_oa_regs(struct intel_vgpu_workload 
*workload,
                 i915_mmio_reg_offset(EU_PERF_CNTL6),
         };

-       if (!workload || !reg_state || workload->ring_id != RCS)
+       if(workload->ring_id != RCS)
                 return;

         if (save) {


Thanks
--
Gustavo