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

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Message-ID: <20180625121844.GA12466@embeddedor.com>
Date:   Mon, 25 Jun 2018 07:18:44 -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

fb is being dereferenced before it is null checked, hence there
is a potential null pointer dereference.

Fix this by moving the pointer dereference after fb has been
properly null checked at line 74: if (!fb)

Addresses-Coverity-ID: 1470169 ("Dereference before null check")
Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 drivers/gpu/drm/gma500/gma_display.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/gma500/gma_display.c b/drivers/gpu/drm/gma500/gma_display.c
index c8f071c..f767579 100644
--- a/drivers/gpu/drm/gma500/gma_display.c
+++ b/drivers/gpu/drm/gma500/gma_display.c
@@ -60,7 +60,7 @@ int gma_pipe_set_base(struct drm_crtc *crtc, int x, int y,
 	struct drm_psb_private *dev_priv = dev->dev_private;
 	struct gma_crtc *gma_crtc = to_gma_crtc(crtc);
 	struct drm_framebuffer *fb = crtc->primary->fb;
-	struct gtt_range *gtt = to_gtt_range(fb->obj[0]);
+	struct gtt_range *gtt;
 	int pipe = gma_crtc->pipe;
 	const struct psb_offset *map = &dev_priv->regmap[pipe];
 	unsigned long start, offset;
@@ -76,6 +76,8 @@ int gma_pipe_set_base(struct drm_crtc *crtc, int x, int y,
 		goto gma_pipe_cleaner;
 	}
 
+	gtt = to_gtt_range(fb->obj[0]);
+
 	/* We are displaying this buffer, make sure it is actually loaded
 	   into the GTT */
 	ret = psb_gtt_pin(gtt);
-- 
2.7.4