linux-kernel - [PATCH] drm/gma500: fix potential NULL pointer dereference dereference

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Message-ID: <20170812015515.GA8360@embeddedgus>
Date:   Fri, 11 Aug 2017 20:55:15 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Patrik Jakobsson <patrik.r.jakobsson@...il.com>,
        David Airlie <airlied@...ux.ie>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] drm/gma500: fix potential NULL pointer dereference
 dereference

NULL check at line 528: if (!sender || !data_out || !len_out) {, implies
that pointer _sender_ might be NULL.

Move pointer _sender_ dereference after NULL check in order to avoid a
potential NULL pointer dereference.

This issue was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 drivers/gpu/drm/gma500/mdfld_dsi_pkg_sender.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/gma500/mdfld_dsi_pkg_sender.c b/drivers/gpu/drm/gma500/mdfld_dsi_pkg_sender.c
index 1616af2..c50534c 100644
--- a/drivers/gpu/drm/gma500/mdfld_dsi_pkg_sender.c
+++ b/drivers/gpu/drm/gma500/mdfld_dsi_pkg_sender.c
@@ -520,7 +520,7 @@ static int __read_panel_data(struct mdfld_dsi_pkg_sender *sender, u8 data_type,
 			u8 *data, u16 len, u32 *data_out, u16 len_out, bool hs)
 {
 	unsigned long flags;
-	struct drm_device *dev = sender->dev;
+	struct drm_device *dev;
 	int i;
 	u32 gen_data_reg;
 	int retry = MDFLD_DSI_READ_MAX_COUNT;
@@ -530,6 +530,8 @@ static int __read_panel_data(struct mdfld_dsi_pkg_sender *sender, u8 data_type,
 		return -EINVAL;
 	}
 
+	dev = sender->dev;
+
 	/**
 	 * do reading.
 	 * 0) send out generic read request
-- 
2.5.0