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Subject[PATCH] stm: ltdc: fix two incorrect NULL checks on list iterator
Date
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);
--
2.17.1
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