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

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Message-ID: <4d850f3c-c199-470f-b83e-00bd9fddbd7a@linux.intel.com>
Date:   Fri, 27 Oct 2023 15:47:43 +0100
From:   Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>
To:     Andrzej Hajda <andrzej.hajda@...el.com>,
        Harshit Mogalapalli <harshit.m.mogalapalli@...cle.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


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.

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;
>>       }
>