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@embeddedor.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180625121844.GA12466@embeddedor.com

diff --git a/drivers/gpu/drm/gma500/gma_display.c b/drivers/gpu/drm/gma500/gma_display.c
index 015dc9f..08f17f8 100644 (file)
--- 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);