On 12/15/2017 09:03 PM, Jordan Crouse wrote:
On Thu, Dec 14, 2017 at 11:11:50AM +0530, Archit Taneja wrote:
The msm/kms driver should work even if there is no GPU device specified
in DT. Currently, we get a NULL dereference crash in adreno_load_gpu
since the driver assumes that priv->gpu_pdev is non-NULL.

Perform an additional check on priv->gpu_pdev before trying to retrieve
the msm_gpu pointer from it.

Fixes: eec874ce5ff1 (drm/msm/adreno: load gpu at probe/bind time)

Signed-off-by: Archit Taneja <arch...@codeaurora.org>
---
  drivers/gpu/drm/msm/adreno/adreno_device.c | 11 +++++++++--
  1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/msm/adreno/adreno_device.c 
b/drivers/gpu/drm/msm/adreno/adreno_device.c
index 05022ea2a007..ac60cf3c794e 100644
--- a/drivers/gpu/drm/msm/adreno/adreno_device.c
+++ b/drivers/gpu/drm/msm/adreno/adreno_device.c
@@ -124,10 +124,17 @@ const struct adreno_info *adreno_info(struct adreno_rev 
rev)
  struct msm_gpu *adreno_load_gpu(struct drm_device *dev)
  {
        struct msm_drm_private *priv = dev->dev_private;
-       struct platform_device *pdev = priv->gpu_pdev;
-       struct msm_gpu *gpu = platform_get_drvdata(priv->gpu_pdev);
+       struct platform_device *pdev;
+       struct msm_gpu *gpu;
        int ret;
+ pdev = priv->gpu_pdev;
+       if (!pdev) {
+               dev_dbg(dev->dev, "no adreno platform device found\n");
+               return NULL;
+       }
+
+       gpu = platform_get_drvdata(pdev);
        if (!gpu) {
                dev_err(dev->dev, "no adreno device\n");
                return NULL;

Obviously correct fix but I can't help but think that we should share the same
error message, so something like:

struct msm_gpu *gpu = NULL;

..

if (priv->gpu_pdev)
    gpu = platform_get_drvdata(priv->gpu_pdev);

if (!gpu) {
        dev_err(dev->dev, "No GPU device was was found\n");
        return NULL;
}

(also, I can't help but think maybe that dev_err should be a ONCE so you don't
get a nasty message every time you open the file descriptor).

This approach looks better. I'll re-spin.

Thanks,
Archit


Jordan


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