drm/radeon/kms/agp The wrong AGP chipset can cause a NULL pointer dereference

Selecting the wrong or no CONFIG_AGP_* chipset can cause a NULL pointer
dereference when combined with CONFIG_DRM_RADEON_KMS and an old system
with a R100 AGP card (should effect other cards too).  The agp field
will be set to NULL if no suitable AGP chipset driver is loaded,
drm_agp_acquire already preforms a suitable NULL check so it can be used
directly.

Signed-off-by: Robert Fitzsimons <robfitz@273k.net>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 4 insertions, 6 deletions

diff --git a/drivers/gpu/drm/radeon/radeon_agp.c b/drivers/gpu/drm/radeon/radeon_agp.c
index c4457791dff1..28e473f1f56f 100644
--- a/drivers/gpu/drm/radeon/radeon_agp.c
+++ b/drivers/gpu/drm/radeon/radeon_agp.c
@@ -134,12 +134,10 @@ int radeon_agp_init(struct radeon_device *rdev)
         int ret;
 
         /* Acquire AGP. */
-        if (!rdev->ddev->agp->acquired) {
-                ret = drm_agp_acquire(rdev->ddev);
-                if (ret) {
-                        DRM_ERROR("Unable to acquire AGP: %d\n", ret);
-                        return ret;
-                }
+        ret = drm_agp_acquire(rdev->ddev);
+        if (ret) {
+                DRM_ERROR("Unable to acquire AGP: %d\n", ret);
+                return ret;
         }
 
         ret = drm_agp_info(rdev->ddev, &info);