drm/radeon: fix race condition UAF in radeon_gem_set_domain_ioctl

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.

Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Min Li <lm0963hack@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/radeon/radeon_gem.c b/drivers/gpu/drm/radeon/radeon_gem.c
index bdc5af2..d3f5ddb 100644 (file)
--- 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;
 }