linux-kernel - [PATCH 5.4 247/453] drm/mediatek: avoid dereferencing a null hdmi

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Date:   Mon, 28 Dec 2020 13:48:03 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Colin Ian King <colin.king@...onical.com>,
        Vinod Koul <vkoul@...nel.org>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 247/453] drm/mediatek: avoid dereferencing a null hdmi_phy on an error message

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

[ Upstream commit b097efba9580d1f7cbc80cda84e768983e3de541 ]

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.

Fixes: be28b6507c46 ("drm/mediatek: separate hdmi phy to different file")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
Addresses-Coverity: ("Dereference after null check")
Link: https://lore.kernel.org/r/20201207150937.170435-1-colin.king@canonical.com
[vkoul: fix indent of return call]
Signed-off-by: Vinod Koul <vkoul@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/mediatek/mtk_hdmi_phy.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_hdmi_phy.c b/drivers/gpu/drm/mediatek/mtk_hdmi_phy.c
index 5223498502c49..23a74eb5d7f81 100644
--- a/drivers/gpu/drm/mediatek/mtk_hdmi_phy.c
+++ b/drivers/gpu/drm/mediatek/mtk_hdmi_phy.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,
-- 
2.27.0