linux-kernel - [PATCH][next] drm/mediatek: avoid dereferencing a null hdmi

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Message-Id: <20201207150937.170435-1-colin.king@canonical.com>
Date:   Mon,  7 Dec 2020 15:09:37 +0000
From:   Colin King <colin.king@...onical.com>
To:     Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Kishon Vijay Abraham I <kishon@...com>,
        Vinod Koul <vkoul@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        CK Hu <ck.hu@...iatek.com>,
        chunhui dai <chunhui.dai@...iatek.com>,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][next] drm/mediatek: avoid dereferencing a null hdmi_phy on an error message

From: Colin Ian King <colin.king@...onical.com>

Currently there is a null pointer check for hdmi_phy that implies it
may be null, however a dev_err messages dereferences this potential null
pointer.  Avoid a null pointer dereference by only emitting the dev_err
message if hdmi_phy is non-null.  It is a moot point if the error message
needs to be printed at all, but since this is a relatively new piece of
code it may be useful to keep the message in for the moment in case there
are unforseen errors that need to be reported.

Addresses-Coverity: ("Dereference after null check")
Fixes: be28b6507c46 ("drm/mediatek: separate hdmi phy to different file")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 drivers/phy/mediatek/phy-mtk-hdmi.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/phy/mediatek/phy-mtk-hdmi.c b/drivers/phy/mediatek/phy-mtk-hdmi.c
index c5c61f5a9ea0..5184054783c7 100644
--- a/drivers/phy/mediatek/phy-mtk-hdmi.c
+++ b/drivers/phy/mediatek/phy-mtk-hdmi.c
@@ -84,8 +84,9 @@ mtk_hdmi_phy_dev_get_ops(const struct mtk_hdmi_phy *hdmi_phy)
 	    hdmi_phy->conf->hdmi_phy_disable_tmds)
 		return &mtk_hdmi_phy_dev_ops;
 
-	dev_err(hdmi_phy->dev, "Failed to get dev ops of phy\n");
-		return NULL;
+	if (hdmi_phy)
+		dev_err(hdmi_phy->dev, "Failed to get dev ops of phy\n");
+			return NULL;
 }
 
 static void mtk_hdmi_phy_clk_get_data(struct mtk_hdmi_phy *hdmi_phy,
-- 
2.29.2