linux-kernel - [PATCH][next] drm/gma500: fix null dereference of pointer fb before null check

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Message-Id: <20191216162136.270114-1-colin.king@canonical.com>
Date:   Mon, 16 Dec 2019 16:21:36 +0000
From:   Colin King <colin.king@...onical.com>
To:     Patrik Jakobsson <patrik.r.jakobsson@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        dri-devel@...ts.freedesktop.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][next] drm/gma500: fix null dereference of pointer fb before null check

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

Pointer fb is being dereferenced when assigning dev before it
is null checked.  Fix this by only dereferencing dev after the
null check.

Fixes: 6b7ce2c4161a ("drm/gma500: Remove struct psb_fbdev")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 drivers/gpu/drm/gma500/accel_2d.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/gma500/accel_2d.c b/drivers/gpu/drm/gma500/accel_2d.c
index b9e5a38632f7..adc0507545bf 100644
--- a/drivers/gpu/drm/gma500/accel_2d.c
+++ b/drivers/gpu/drm/gma500/accel_2d.c
@@ -228,8 +228,8 @@ static void psbfb_copyarea_accel(struct fb_info *info,
 {
 	struct drm_fb_helper *fb_helper = info->par;
 	struct drm_framebuffer *fb = fb_helper->fb;
-	struct drm_device *dev = fb->dev;
-	struct drm_psb_private *dev_priv = dev->dev_private;
+	struct drm_device *dev;
+	struct drm_psb_private *dev_priv;
 	uint32_t offset;
 	uint32_t stride;
 	uint32_t src_format;
@@ -238,6 +238,8 @@ static void psbfb_copyarea_accel(struct fb_info *info,
 	if (!fb)
 		return;
 
+	dev = fb->dev;
+	dev_priv = dev->dev_private;
 	offset = to_gtt_range(fb->obj[0])->offset;
 	stride = fb->pitches[0];
 
-- 
2.24.0