linux-kernel - [PATCH AUTOSEL 5.4 6/6] drm/amd/display: Avoid NULL dereference of timing generator

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Message-ID: <20231112132902.176672-6-sashal@kernel.org>
Date:   Sun, 12 Nov 2023 08:29:00 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Wayne Lin <wayne.lin@....com>, Jun Lei <jun.lei@....com>,
        Hersen Wu <hersenxs.wu@....com>,
        Daniel Wheeler <daniel.wheeler@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>, christian.koenig@....com,
        airlied@...ux.ie, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 5.4 6/6] drm/amd/display: Avoid NULL dereference of timing generator

From: Wayne Lin <wayne.lin@....com>

[ Upstream commit b1904ed480cee3f9f4036ea0e36d139cb5fee2d6 ]

[Why & How]
Check whether assigned timing generator is NULL or not before
accessing its funcs to prevent NULL dereference.

Reviewed-by: Jun Lei <jun.lei@....com>
Acked-by: Hersen Wu <hersenxs.wu@....com>
Signed-off-by: Wayne Lin <wayne.lin@....com>
Tested-by: Daniel Wheeler <daniel.wheeler@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/amd/display/dc/core/dc_stream.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_stream.c b/drivers/gpu/drm/amd/display/dc/core/dc_stream.c
index bb09243758fe3..71b10b45a9b9e 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_stream.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_stream.c
@@ -492,7 +492,7 @@ uint32_t dc_stream_get_vblank_counter(const struct dc_stream_state *stream)
 	for (i = 0; i < MAX_PIPES; i++) {
 		struct timing_generator *tg = res_ctx->pipe_ctx[i].stream_res.tg;
 
-		if (res_ctx->pipe_ctx[i].stream != stream)
+		if (res_ctx->pipe_ctx[i].stream != stream || !tg)
 			continue;
 
 		return tg->funcs->get_frame_count(tg);
@@ -551,7 +551,7 @@ bool dc_stream_get_scanoutpos(const struct dc_stream_state *stream,
 	for (i = 0; i < MAX_PIPES; i++) {
 		struct timing_generator *tg = res_ctx->pipe_ctx[i].stream_res.tg;
 
-		if (res_ctx->pipe_ctx[i].stream != stream)
+		if (res_ctx->pipe_ctx[i].stream != stream || !tg)
 			continue;
 
 		tg->funcs->get_scanoutpos(tg,
-- 
2.42.0