linux-kernel - Re: [Freedreno] [PATCH] drm/msm: correct NULL pointer dereference in context_init

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Message-ID: <20190722182222.GG104440@art_vandelay>
Date:   Mon, 22 Jul 2019 14:22:22 -0400
From:   Sean Paul <sean@...rly.run>
To:     Rob Clark <robdclark@...il.com>
Cc:     Brian Masney <masneyb@...tation.org>,
        Jordan Crouse <jcrouse@...eaurora.org>,
        Rob Clark <robdclark@...omium.org>,
        Sean Paul <seanpaul@...omium.org>,
        Jean-Philippe Brucker <jean-philippe.brucker@....com>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Douglas Anderson <dianders@...omium.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        David Airlie <airlied@...ux.ie>,
        "Kristian H. Kristensen" <hoegsberg@...gle.com>,
        Daniel Vetter <daniel@...ll.ch>,
        freedreno <freedreno@...ts.freedesktop.org>
Subject: Re: [Freedreno] [PATCH] drm/msm: correct NULL pointer dereference in
 context_init

On Fri, Jun 28, 2019 at 05:57:26AM -0700, Rob Clark wrote:
> On Wed, Jun 26, 2019 at 7:05 PM Brian Masney <masneyb@...tation.org> wrote:
> >
> > Correct attempted NULL pointer dereference in context_init() when
> > running without an IOMMU.
> >
> > Signed-off-by: Brian Masney <masneyb@...tation.org>
> > Fixes: 295b22ae596c ("drm/msm: Pass the MMU domain index in struct msm_file_private")
> > ---
> > The no IOMMU case seems like functionality that we may want to keep
> > based on this comment:
> > https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/msm/adreno/a3xx_gpu.c#L523
> > Once I get the msm8974 interconnect driver done, I'm going to look into
> > what needs to be done to get the IOMMU working on the Nexus 5.
> >
> > Alternatively, for development purposes, maybe we could have a NOOP
> > IOMMU driver that would allow us to remove these NULL checks that are
> > sprinkled throughout the code. I haven't looked into this in detail.
> > Thoughts?
> 
> yeah, we probably want to keep !iommu support, it is at least useful
> for bringup of new (or old) devices.  But tends to bitrot a since it
> isn't a case that gets tested much once iommu is in place.  Perhaps
> there is a way to have a null iommu/aspace, although I'm not quite
> sure how that would work..
> 
> Anyways,
> 
> Reviewed-by: Rob Clark <robdclark@...il.com>
> 
> (I guess this can go in via drm-misc-fixes unless we get some more
> fixes to justify sending msm-fixes MR..)

Applied to drm-misc-fixes for 5.3

Sean

> 
> >
> >  drivers/gpu/drm/msm/msm_drv.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
> > index 451bd4508793..83047cb2c735 100644
> > --- a/drivers/gpu/drm/msm/msm_drv.c
> > +++ b/drivers/gpu/drm/msm/msm_drv.c
> > @@ -619,7 +619,7 @@ static int context_init(struct drm_device *dev, struct drm_file *file)
> >
> >         msm_submitqueue_init(dev, ctx);
> >
> > -       ctx->aspace = priv->gpu->aspace;
> > +       ctx->aspace = priv->gpu ? priv->gpu->aspace : NULL;
> >         file->driver_priv = ctx;
> >
> >         return 0;
> > --
> > 2.20.1
> >
> > _______________________________________________
> > Freedreno mailing list
> > Freedreno@...ts.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/freedreno

-- 
Sean Paul, Software Engineer, Google / Chromium OS

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