linux-kernel - Re: [PATCH] i915/perf: Fix NULL deref bugs with drm

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Date:   Fri, 27 Oct 2023 22:48:45 +0530
From:   Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
To:     Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Umesh Nerlige Ramappa <umesh.nerlige.ramappa@...el.com>,
        Lionel Landwerlin <lionel.g.landwerlin@...el.com>,
        Matt Roper <matthew.d.roper@...el.com>,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Cc:     dan.carpenter@...aro.org, kernel-janitors@...r.kernel.org,
        error27@...il.com
Subject: Re: [PATCH] i915/perf: Fix NULL deref bugs with drm_dbg() calls

Hi Tvrtko,

On 27/10/23 8:17 pm, Tvrtko Ursulin wrote:
> 
> On 27/10/2023 15:11, Andrzej Hajda wrote:
>> On 27.10.2023 16:07, Harshit Mogalapalli wrote:
>>> When i915 perf interface is not available dereferencing it will lead to
>>> NULL dereferences.
>>>
>>> Fix this by using DRM_DEBUG() which the scenario before the commit in
>>> the Fixes tag.
>>>
>>> Fixes: 2fec539112e8 ("i915/perf: Replace DRM_DEBUG with driver 
>>> specific drm_dbg call")
>>> Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
>>
>>
>> Reviewed-by: Andrzej Hajda <andrzej.hajda@...el.com>
> 
> Please hold off merging.
> 
>>> ---
>>> This is found using smatch(static analysis tool), only compile tested.
>>> ---
>>>   drivers/gpu/drm/i915/i915_perf.c | 9 +++------
>>>   1 file changed, 3 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/i915_perf.c 
>>> b/drivers/gpu/drm/i915/i915_perf.c
>>> index 2f3ecd7d4804..bb48c96b7950 100644
>>> --- a/drivers/gpu/drm/i915/i915_perf.c
>>> +++ b/drivers/gpu/drm/i915/i915_perf.c
>>> @@ -4228,8 +4228,7 @@ int i915_perf_open_ioctl(struct drm_device 
>>> *dev, void *data,
>>>       int ret;
>>>       if (!perf->i915) {
>>> -        drm_dbg(&perf->i915->drm,
>>> -            "i915 perf interface not available for this system\n");
>>> +        DRM_DEBUG("i915 perf interface not available for this 
>>> system\n");
> 
> What's that struct drm_device *dev function argument a few lines up? :)
> 
> Although TBH all these these could just be removed since I doubt they 
> are adding any value and ENOTSUPP is pretty clear.
> 

Thanks for checking. I will remove the dbg() calls and send a V2.

Regards,
Harshit

> Regards,
> 
> Tvrtko
> 
>>>           return -ENOTSUPP;
>>>       }
>>> @@ -4608,8 +4607,7 @@ int i915_perf_add_config_ioctl(struct 
>>> drm_device *dev, void *data,
>>>       int err, id;
>>>       if (!perf->i915) {
>>> -        drm_dbg(&perf->i915->drm,
>>> -            "i915 perf interface not available for this system\n");
>>> +        DRM_DEBUG("i915 perf interface not available for this 
>>> system\n");
>>>           return -ENOTSUPP;
>>>       }
>>> @@ -4774,8 +4772,7 @@ int i915_perf_remove_config_ioctl(struct 
>>> drm_device *dev, void *data,
>>>       int ret;
>>>       if (!perf->i915) {
>>> -        drm_dbg(&perf->i915->drm,
>>> -            "i915 perf interface not available for this system\n");
>>> +        DRM_DEBUG("i915 perf interface not available for this 
>>> system\n");
>>>           return -ENOTSUPP;
>>>       }
>>