linux-kernel - Re: [PATCH v2] drm/radeon: fix race condition UAF in radeon_gem_set_domain

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Date:   Mon, 5 Jun 2023 11:21:58 -0400
From:   Alex Deucher <alexdeucher@...il.com>
To:     Christian König <christian.koenig@....com>
Cc:     Min Li <lm0963hack@...il.com>, alexander.deucher@....com,
        Xinhui.Pan@....com, linux-kernel@...r.kernel.org,
        amd-gfx@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org,
        dri-devel@...ts.freedesktop.org, sumit.semwal@...aro.org,
        linux-media@...r.kernel.org
Subject: Re: [PATCH v2] drm/radeon: fix race condition UAF in radeon_gem_set_domain_ioctl

Applied.  Thanks!

On Mon, Jun 5, 2023 at 4:13 AM Christian König <christian.koenig@....com> wrote:
>
> Am 03.06.23 um 09:43 schrieb Min Li:
> > Userspace can race to free the gobj(robj converted from), robj should not
> > be accessed again after drm_gem_object_put, otherwith it will result in
> > use-after-free.
> >
> > Signed-off-by: Min Li <lm0963hack@...il.com>
>
> Reviewed-by: Christian König <christian.koenig@....com>
>
> > ---
> > Changes in v2:
> > - Remove unused robj, avoid compile complain
> >
> >   drivers/gpu/drm/radeon/radeon_gem.c | 4 +---
> >   1 file changed, 1 insertion(+), 3 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/radeon/radeon_gem.c b/drivers/gpu/drm/radeon/radeon_gem.c
> > index bdc5af23f005..d3f5ddbc1704 100644
> > --- a/drivers/gpu/drm/radeon/radeon_gem.c
> > +++ b/drivers/gpu/drm/radeon/radeon_gem.c
> > @@ -459,7 +459,6 @@ int radeon_gem_set_domain_ioctl(struct drm_device *dev, void *data,
> >       struct radeon_device *rdev = dev->dev_private;
> >       struct drm_radeon_gem_set_domain *args = data;
> >       struct drm_gem_object *gobj;
> > -     struct radeon_bo *robj;
> >       int r;
> >
> >       /* for now if someone requests domain CPU -
> > @@ -472,13 +471,12 @@ int radeon_gem_set_domain_ioctl(struct drm_device *dev, void *data,
> >               up_read(&rdev->exclusive_lock);
> >               return -ENOENT;
> >       }
> > -     robj = gem_to_radeon_bo(gobj);
> >
> >       r = radeon_gem_set_domain(gobj, args->read_domains, args->write_domain);
> >
> >       drm_gem_object_put(gobj);
> >       up_read(&rdev->exclusive_lock);
> > -     r = radeon_gem_handle_lockup(robj->rdev, r);
> > +     r = radeon_gem_handle_lockup(rdev, r);
> >       return r;
> >   }
> >
>