On 27/03/2022 10:32, Xiaomeng Tong wrote:
The bug is here:
cstate = to_dpu_crtc_state(drm_crtc->state);
For the drm_for_each_crtc(), just like list_for_each_entry(),
the list iterator 'drm_crtc' will point to a bogus position
containing HEAD if the list is empty or no element is found.
This case must be checked before any use of the iterator,
otherwise it will lead to a invalid memory access.
To fix this bug, use a new variable 'iter' as the list iterator,
while use the origin variable 'drm_crtc' as a dedicated pointer
to point to the found element.
Cc: stable@xxxxxxxxxxxxxxx
Fixes: b107603b4ad0f ("drm/msm/dpu: map mixer/ctl hw blocks in encoder modeset")
Signed-off-by: Xiaomeng Tong <xiam0nd.tong@xxxxxxxxx>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
---
drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
index 1e648db439f9..d3fdb18e96f9 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
@@ -965,7 +965,7 @@ static void dpu_encoder_virt_mode_set(struct drm_encoder *drm_enc,
struct dpu_kms *dpu_kms;
struct list_head *connector_list;
struct drm_connector *conn = NULL, *conn_iter;
- struct drm_crtc *drm_crtc;
+ struct drm_crtc *drm_crtc = NULL, *iter;
struct dpu_crtc_state *cstate;
struct dpu_global_state *global_state;
struct dpu_hw_blk *hw_pp[MAX_CHANNELS_PER_ENC];
@@ -1007,9 +1007,14 @@ static void dpu_encoder_virt_mode_set(struct drm_encoder *drm_enc,
return;
}
- drm_for_each_crtc(drm_crtc, drm_enc->dev)
- if (drm_crtc->state->encoder_mask & drm_encoder_mask(drm_enc))
+ drm_for_each_crtc(iter, drm_enc->dev)
+ if (iter->state->encoder_mask & drm_encoder_mask(drm_enc)) {
+ drm_crtc = iter;
break;
+ }
+
+ if (!drm_crtc)
+ return;
/* Query resource that have been reserved in atomic check step. */
num_pp = dpu_rm_get_assigned_resources(&dpu_kms->rm, global_state,
--
With best wishes
Dmitry
