The two bugs are here: if (encoder) { if (bridge && bridge->timings)

The list iterator value 'encoder/bridge' will *always* be set and non-NULL by drm_for_each_encoder()/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 old variable 'encoder/bridge' as a dedicated pointer to point to the found element.

Cc: stable@vger.kernel.org Fixes: 99e360442f223 ("drm/stm: Fix bus_flags handling") Signed-off-by: Xiaomeng Tong xiam0nd.tong@gmail.com --- drivers/gpu/drm/stm/ltdc.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c index dbdee954692a..d6124aa873e5 100644 --- a/drivers/gpu/drm/stm/ltdc.c +++ b/drivers/gpu/drm/stm/ltdc.c @@ -528,8 +528,8 @@ static void ltdc_crtc_mode_set_nofb(struct drm_crtc *crtc) struct drm_device *ddev = crtc->dev; struct drm_connector_list_iter iter; struct drm_connector *connector = NULL; - struct drm_encoder *encoder = NULL; - struct drm_bridge *bridge = NULL; + struct drm_encoder *encoder = NULL, *en_iter; + struct drm_bridge *bridge = NULL, *br_iter; struct drm_display_mode *mode = &crtc->state->adjusted_mode; u32 hsync, vsync, accum_hbp, accum_vbp, accum_act_w, accum_act_h; u32 total_width, total_height; @@ -538,15 +538,19 @@ static void ltdc_crtc_mode_set_nofb(struct drm_crtc *crtc) int ret;

/* get encoder from crtc */ - drm_for_each_encoder(encoder, ddev) - if (encoder->crtc == crtc) + drm_for_each_encoder(en_iter, ddev) + if (en_iter->crtc == crtc) { + encoder = en_iter; break; + }

if (encoder) { /* get bridge from encoder */ - list_for_each_entry(bridge, &encoder->bridge_chain, chain_node) - if (bridge->encoder == encoder) + list_for_each_entry(br_iter, &encoder->bridge_chain, chain_node) + if (br_iter->encoder == encoder) { + bridge = br_iter; break; + }

/* Get the connector from encoder */ drm_connector_list_iter_begin(ddev, &iter);