soc: qcom: ocmem: don't return NULL in of_get_ocmem

[ Upstream commit 01f937f ]

If ocmem probe fails for whatever reason, of_get_ocmem returned NULL.
Without this, users must check for both NULL and IS_ERR on the returned
pointer - which didn't happen in drivers/gpu/drm/msm/adreno/adreno_gpu.c
leading to a NULL pointer dereference.

Reviewed-by: Brian Masney <masneyb@onstation.org>
Fixes: 88c1e94 ("soc: qcom: add OCMEM driver")
Signed-off-by: Luca Weiss <luca@z3ntu.xyz>
Link: https://lore.kernel.org/r/20210130142349.53335-1-luca@z3ntu.xyz
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/soc/qcom/ocmem.c

@@ -189,6 +189,7 @@ struct ocmem *of_get_ocmem(struct device *dev)
 {
 	struct platform_device *pdev;
 	struct device_node *devnode;
+	struct ocmem *ocmem;
 
 	devnode = of_parse_phandle(dev->of_node, "sram", 0);
 	if (!devnode || !devnode->parent) {
@@ -202,7 +203,12 @@ struct ocmem *of_get_ocmem(struct device *dev)
 		return ERR_PTR(-EPROBE_DEFER);
 	}
 
-	return platform_get_drvdata(pdev);
+	ocmem = platform_get_drvdata(pdev);
+	if (!ocmem) {
+		dev_err(dev, "Cannot get ocmem\n");
+		return ERR_PTR(-ENODEV);
+	}
+	return ocmem;
 }
 EXPORT_SYMBOL(of_get_ocmem);