[bug report] drm/prime: replace NULL with error value in drm_prime_pages_to_sg

[Dan Carpenter]

On Fri, Jun 15, 2018 at 08:39:17AM +0300, Oleksandr Andrushchenko wrote:
> On 06/15/2018 06:22 AM, YoungJun Cho wrote:
> > Dear Dan,
> > 
> > Your mail flashes back to my memory 5 years ago.
> > Back then, I had cleaned up the exynos driver.
> > 
> > And the replacement IS_ERR was one of items.
> > 
> > IMHO it is still better to modify those two functions,
> > drm_gem_cma_prime_get_sg_table and xen_drm_front_gem_get_sg_table.
> > 
> > Thank you.
> > Best regards YJ
> > 
> > 
> > On Thu, 14 Jun 2018, 23:42 Dan Carpenter, <dan.carpenter at oracle.com
> > <mailto:dan.carpenter at oracle.com>> wrote:
> > 
> >     Hello YoungJun Cho,
> > 
> >     The patch 7e3d88f9cce3: "drm/prime: replace NULL with error value in
> >     drm_prime_pages_to_sg" from Jun 24, 2013, leads to the following
> >     static checker warning:
> > 
> >             drivers/gpu/drm/drm_prime.c:317 drm_gem_map_dma_buf()
> >             warn: 'sgt' can also be NULL
> > 
> >     drivers/gpu/drm/drm_prime.c
> >        307          /*
> >        308           * two mappings with different directions for the
> >     same attachment are
> >        309           * not allowed
> >        310           */
> >        311          if (WARN_ON(prime_attach->dir != DMA_NONE))
> >        312                  return ERR_PTR(-EBUSY);
> >        313
> >        314          sgt = obj->dev->driver->gem_prime_get_sg_table(obj);
> > 
> >     The problematic functions here are
> >     drm_gem_cma_prime_get_sg_table() and
> >     xen_drm_front_gem_get_sg_table().  My preference would be to update
> >     those functions to return error pointers, but I'm not familiar
> >     with the
> >     code or able to test it.
> > 
> I believe it is safe to change the return value to error pointer:
> the code below (which is the only caller of .gem_prime_get_sg_table
> callback) does not check for NULL anyways
> 
> Dan, do you want me to send the patch for Xen or you prefer to post both
> Xen and CMA helpers fix yourself?

Can you do it and give me a Reported-by tag?

regards,
dan carpenter