drm/amd/display: Skip accessing array for unknown eng_id

[WHY]
ENGINE_ID_UNKNOWN (-1) is not a valid eng_id and not a valid array
index.

[HOW]
Check whether eng_id is unknown to avoid access array with negative
array index.

This fixes 4 OVERRUN issues reported by Coverity.

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_enc_cfg.c b/drivers/gpu/drm/amd/display/dc/core/dc_link_enc_cfg.c
index be5a6d0..039b176 100644 (file)
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link_enc_cfg.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_enc_cfg.c
@@ -248,6 +248,8 @@ static struct link_encoder *get_link_enc_used_by_link(
 
        for (i = 0; i < MAX_PIPES; i++) {
                struct link_enc_assignment assignment = state->res_ctx.link_enc_cfg_ctx.link_enc_assignments[i];
+               if (assignment.eng_id == ENGINE_ID_UNKNOWN)
+                       continue;
 
                if (assignment.valid == true && are_ep_ids_equal(&assignment.ep_id, &ep_id))
                        link_enc = link->dc->res_pool->link_encoders[assignment.eng_id - ENGINE_ID_DIGA];
@@ -517,6 +519,8 @@ struct link_encoder *link_enc_cfg_get_link_enc_used_by_link(
 
        for (i = 0; i < MAX_PIPES; i++) {
                struct link_enc_assignment assignment = get_assignment(dc, i);
+               if (assignment.eng_id == ENGINE_ID_UNKNOWN)
+                       continue;
 
                if (assignment.valid == true && are_ep_ids_equal(&assignment.ep_id, &ep_id)) {
                        link_enc = link->dc->res_pool->link_encoders[assignment.eng_id - ENGINE_ID_DIGA];
@@ -540,7 +544,7 @@ struct link_encoder *link_enc_cfg_get_next_avail_link_enc(struct dc *dc)
        for (i = 0; i < MAX_PIPES; i++) {
                struct link_enc_assignment assignment = get_assignment(dc, i);
 
-               if (assignment.valid)
+               if (assignment.valid && assignment.eng_id != ENGINE_ID_UNKNOWN)
                        encs_assigned[assignment.eng_id - ENGINE_ID_DIGA] = assignment.eng_id;
        }
 
@@ -602,6 +606,9 @@ struct link_encoder *link_enc_cfg_get_link_enc_used_by_stream_current(
                struct link_enc_assignment assignment =
                        dc->current_state->res_ctx.link_enc_cfg_ctx.link_enc_assignments[i];
 
+               if (assignment.eng_id == ENGINE_ID_UNKNOWN)
+                       continue;
+
                if (assignment.valid == true && are_ep_ids_equal(&assignment.ep_id, &ep_id)) {
                        link_enc = stream->link->dc->res_pool->link_encoders[assignment.eng_id - ENGINE_ID_DIGA];
                        break;