drm/fb_helper: Fix potential NULL pointer dereference

kcalloc returns NULL on failure. Hence check for the return value
and exit on error to avoid NULL pointer dereference.

Fixes the following smatch errors:
drivers/gpu/drm/drm_fb_helper.c:1271 drm_setup_crtcs() error:
potential null dereference 'modes'.  (kcalloc returns null)
drivers/gpu/drm/drm_fb_helper.c:1272 drm_setup_crtcs() error:
potential null dereference 'crtcs'.  (kcalloc returns null)

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 8c2de020e8eb..2c44af691e98 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -1251,6 +1251,11 @@ static void drm_setup_crtcs(struct drm_fb_helper *fb_helper)
                         sizeof(struct drm_display_mode *), GFP_KERNEL);
         enabled = kcalloc(dev->mode_config.num_connector,
                           sizeof(bool), GFP_KERNEL);
+        if (!crtcs || !modes || !enabled) {
+                DRM_ERROR("Memory allocation failed\n");
+                goto out;
+        }
+
 
         drm_enable_connectors(fb_helper, enabled);
 
@@ -1289,6 +1294,7 @@ static void drm_setup_crtcs(struct drm_fb_helper *fb_helper)
                 }
         }
 
+out:
         kfree(crtcs);
         kfree(modes);
         kfree(enabled);