Re: [PATCH v5 3/3] drm: protect drm_master pointers in drm_lease.c

[Desmond Cheong Zhi Xi]

On 30/6/21 8:16 am, Emil Velikov wrote:
Hi Desmond,
Couple of small suggestions, with those the series is:
Reviewed-by: Emil Velikov <emil.l.veli...@gmail.com>

On Tue, 29 Jun 2021 at 04:38, Desmond Cheong Zhi Xi
<desmondcheon...@gmail.com> wrote:

@@ -128,13 +137,20 @@ bool drm_lease_held(struct drm_file *file_priv, int id)
         struct drm_master *master;
         bool ret;

-       if (!file_priv || !file_priv->master || !file_priv->master->lessor)
+       if (!file_priv)
                 return true;

-       master = file_priv->master;
+       master = drm_file_get_master(file_priv);
+       if (master == NULL)
+               return true;
+       if (!master->lessor) {
+               drm_master_put(&master);
+               return true;

Let's add a "ret = true; goto unlock;" here, so we can have a single
drm_master_put() in the function.
Nearly all code paths touched by this patch already follow this approach.

@@ -154,10 +170,16 @@ uint32_t drm_lease_filter_crtcs(struct drm_file 
*file_priv, uint32_t crtcs_in)
         int count_in, count_out;
         uint32_t crtcs_out = 0;

-       if (!file_priv || !file_priv->master || !file_priv->master->lessor)
+       if (!file_priv)
                 return crtcs_in;

-       master = file_priv->master;
+       master = drm_file_get_master(file_priv);
+       if (master == NULL)
+               return crtcs_in;
+       if (!master->lessor) {
+               drm_master_put(&master);
+               return crtcs_in;

Ditto

Thanks
Emil


Sounds good to me, I'll revise these functions. Thanks for the review 
and suggestions, Emil.

Best wishes,
Desmond