[PATCH 6.1.y] drm/amd/display: Validate function returns

[Artem Dinaburg]

From: Alex Hung <alex.hung@xxxxxxx>

[ Upstream commit 673f816b9e1e92d1f70e1bf5f21b531e0ff9ad6c ]

[WHAT & HOW]
Function return values must be checked before data can be used
in subsequent functions.

This fixes 4 CHECKED_RETURN issues reported by Coverity.

[ Backport to 6.1.y: adapted the visual-panel, watermark, and
  link-detection checks to their older locations. The upstream DMUB
  run-list/D3 path is absent; the older dc_dmub_srv_cmd_queue() already
  checks and logs idle-wait failures but, unlike upstream, still retries
  the queue once afterwards. No DMUB queue change is included. ]

Reviewed-by: Harry Wentland <harry.wentland@xxxxxxx>
Signed-off-by: Alex Hung <alex.hung@xxxxxxx>
Tested-by: Daniel Wheeler <daniel.wheeler@xxxxxxx>
Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
Assisted-by: LLM
Signed-off-by: Artem Dinaburg <artem@xxxxxxxxxxxxxxx>
---
Hi Greg, Sasha, and drm amd maintainers,

I am working through the small CVE backports still missing from 6.1.y.
This one addresses CVE-2024-46775. It carries the three return-value
checks that map to 6.1.y: visual-panel validation, p-state watermark
propagation, and sink-detection validation during link-training retries.

The upstream DMUB run-list/D3 path does not exist here. I left 6.1.y's
older dc_dmub_srv_cmd_queue() unchanged. It already checks and logs the
idle-wait result, but unlike upstream it still re-queues once after a
failed wait, and checks that re-queue's status.

The corresponding 6.6.y backport is already in the 6.6.y stable queue.
The fix is already present in 6.12.y, 6.18.y, and 7.2.y, but not
in 6.1.y.
The target-specific adjustment is recorded in the bracketed note above.

Could you please queue it for 6.1.y?

CVE: CVE-2024-46775
Upstream: 673f816b9e1e92d1f70e1bf5f21b531e0ff9ad6c

AI assistance: An LLM helped identify, adapt, and validate this backport; I
reviewed the resulting code and validation evidence.

Thanks,
Artem Dinaburg

 drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c    | 3 +--
 drivers/gpu/drm/amd/display/dc/dc_dmub_srv.c        | 3 ++-
 drivers/gpu/drm/amd/display/dc/dcn20/dcn20_hubbub.c | 3 ++-
 3 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
index 82b747c0ed693b..1d3d9a82c4637d 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
@@ -2808,8 +2808,7 @@ bool perform_link_training_with_retries(
 		if (status == LINK_TRAINING_ABORT) {
 			enum dc_connection_type type = dc_connection_none;
 
-			dc_link_detect_sink(link, &type);
-			if (type == dc_connection_none) {
+			if (dc_link_detect_sink(link, &type) && type == dc_connection_none) {
 				DC_LOG_HW_LINK_TRAINING("%s: Aborting training because sink unplugged\n", __func__);
 				break;
 			}
diff --git a/drivers/gpu/drm/amd/display/dc/dc_dmub_srv.c b/drivers/gpu/drm/amd/display/dc/dc_dmub_srv.c
index 31bb7e782c6b1d..35e8f22d30204b 100644
--- a/drivers/gpu/drm/amd/display/dc/dc_dmub_srv.c
+++ b/drivers/gpu/drm/amd/display/dc/dc_dmub_srv.c
@@ -396,7 +396,8 @@ void dc_dmub_srv_get_visual_confirm_color_cmd(struct dc *dc, struct pipe_ctx *pi
 	enum dmub_status status;
 	unsigned int panel_inst = 0;
 
-	dc_get_edp_link_panel_inst(dc, pipe_ctx->stream->link, &panel_inst);
+	if (!dc_get_edp_link_panel_inst(dc, pipe_ctx->stream->link, &panel_inst))
+		return;
 
 	memset(&cmd, 0, sizeof(cmd));
 
diff --git a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_hubbub.c b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_hubbub.c
index aacb1fb5c73eb5..d2eebe39a55e33 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_hubbub.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_hubbub.c
@@ -595,7 +595,8 @@ static bool hubbub2_program_watermarks(
 		hubbub1->base.ctx->dc->clk_mgr->clks.p_state_change_support == false)
 		safe_to_lower = true;
 
-	hubbub1_program_pstate_watermarks(hubbub, watermarks, refclk_mhz, safe_to_lower);
+	if (hubbub1_program_pstate_watermarks(hubbub, watermarks, refclk_mhz, safe_to_lower))
+		wm_pending = true;
 
 	REG_SET(DCHUBBUB_ARB_SAT_LEVEL, 0,
 			DCHUBBUB_ARB_SAT_LEVEL, 60 * refclk_mhz);
-- 
2.39.5