On 2022-03-27 9:15, Xiaomeng Tong wrote:

The bug is here: if (!encoder) {

The list iterator value 'encoder' will *always* be set and non-NULL by list_for_each_entry(), so it is incorrect to assume that the iterator value will be NULL if the list is empty or no element is found.

To fix the bug, use a new variable 'iter' as the list iterator, while use the original variable 'encoder' as a dedicated pointer to point to the found element.

Cc: stable@vger.kernel.org Fixes: ec9eab097a500 ("drm/tilcdc: Add drm bridge support for attaching drm bridge drivers") Signed-off-by: Xiaomeng Tong xiam0nd.tong@gmail.com

Thanks for the patch. Good catch.

Reviewed-by: Jyri Sarha jyri.sarha@iki.fi Tested-by: Jyri Sarha jyri.sarha@iki.fi

I'll apply this to drm-misc-next in couple of days.

Best regards, Jyri

---

drivers/gpu/drm/tilcdc/tilcdc_external.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/tilcdc/tilcdc_external.c b/drivers/gpu/drm/tilcdc/tilcdc_external.c index 7594cf6e186e..3b86d002ef62 100644 --- a/drivers/gpu/drm/tilcdc/tilcdc_external.c +++ b/drivers/gpu/drm/tilcdc/tilcdc_external.c @@ -60,11 +60,13 @@ struct drm_connector *tilcdc_encoder_find_connector(struct drm_device *ddev, int tilcdc_add_component_encoder(struct drm_device *ddev) { struct tilcdc_drm_private *priv = ddev->dev_private;

• struct drm_encoder *encoder;

• struct drm_encoder *encoder = NULL, *iter;

• list_for_each_entry(encoder, &ddev->mode_config.encoder_list, head)

• if (encoder->possible_crtcs & (1 << priv->crtc->index))
  

• list_for_each_entry(iter, &ddev->mode_config.encoder_list, head)

• if (iter->possible_crtcs & (1 << priv->crtc->index)) {
  

• 	encoder = iter;
  break;
  

• }
  
  

  if (!encoder) { dev_err(ddev->dev, "%s: No suitable encoder found\n", __func__);