linux-kernel - [PATCH 6.6.y] drm/amd/display: Check link

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Message-ID: <20250408003647.3361342-1-jianqi.ren.cn@windriver.com>
Date: Tue, 8 Apr 2025 08:36:47 +0800
From: <jianqi.ren.cn@...driver.com>
To: <stable@...r.kernel.org>
CC: <patches@...ts.linux.dev>, <gregkh@...uxfoundation.org>,
        <linux-kernel@...r.kernel.org>, <jianqi.ren.cn@...driver.com>,
        <harry.wentland@....com>, <sunpeng.li@....com>,
        <Rodrigo.Siqueira@....com>, <alexander.deucher@....com>,
        <christian.koenig@....com>, <Xinhui.Pan@....com>, <airlied@...il.com>,
        <daniel@...ll.ch>, <amd-gfx@...ts.freedesktop.org>,
        <dri-devel@...ts.freedesktop.org>, <chiahsuan.chung@....com>,
        <alex.hung@....com>, <daniel.wheeler@....com>
Subject: [PATCH 6.6.y] drm/amd/display: Check link_index before accessing dc->links[]

From: Alex Hung <alex.hung@....com>

[ Upstream commit 8aa2864044b9d13e95fe224f32e808afbf79ecdf ]

[WHY & HOW]
dc->links[] has max size of MAX_LINKS and NULL is return when trying to
access with out-of-bound index.

This fixes 3 OVERRUN and 1 RESOURCE_LEAK issues reported by Coverity.

Reviewed-by: Harry Wentland <harry.wentland@....com>
Acked-by: Tom Chung <chiahsuan.chung@....com>
Signed-off-by: Alex Hung <alex.hung@....com>
Tested-by: Daniel Wheeler <daniel.wheeler@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
[The macro MAX_LINKS is introduced by Commit 60df5628144b ("drm/amd/display:
 handle invalid connector indices") after 6.10. So here we still use the
 original array length MAX_PIPES * 2]
Signed-off-by: Jianqi Ren <jianqi.ren.cn@...driver.com>
Signed-off-by: He Zhe <zhe.he@...driver.com>
---
Verified the build test
---
 drivers/gpu/drm/amd/display/dc/core/dc_link_exports.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_exports.c b/drivers/gpu/drm/amd/display/dc/core/dc_link_exports.c
index f365773d5714..e9b3c1c7a931 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link_exports.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_exports.c
@@ -37,6 +37,9 @@
 #include "dce/dce_i2c.h"
 struct dc_link *dc_get_link_at_index(struct dc *dc, uint32_t link_index)
 {
+	if (link_index >= (MAX_PIPES * 2))
+		return NULL;
+
 	return dc->links[link_index];
 }
 
-- 
2.34.1