Re: [PATCH] i915/perf: Fix NULL deref bugs with drm_dbg() calls

[Harshit Mogalapalli]

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@xxxxxxxxxx>
> >
> >
> > Reviewed-by: Andrzej Hajda <andrzej.hajda@xxxxxxxxx>
>
> 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;
> > >       }