iommu/mediatek: Use correct fwspec in mtk_iommu_add_device()

The mtk_iommu_add_device() function keeps the fwspec in an
on-stack pointer and calls mtk_iommu_create_mapping(), which
might change its source, dev->iommu_fwspec. This causes the
on-stack pointer to be obsoleted and the device
initialization to fail. Update the on-stack fwspec pointer
after mtk_iommu_create_mapping() has been called.

Reported-by: Frank Wunderlich <frank-w@public-files.de>
Fixes: a9bf2ee ('iommu/mediatek: Use helper functions to access dev->iommu_fwspec')
Tested-by: Frank Wunderlich <frank-w@public-files.de>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/mtk_iommu_v1.c

@@ -442,6 +442,10 @@ static int mtk_iommu_add_device(struct device *dev)
 		iommu_spec.args_count = count;
 
 		mtk_iommu_create_mapping(dev, &iommu_spec);
+
+		/* dev->iommu_fwspec might have changed */
+		fwspec = dev_iommu_fwspec_get(dev);
+
 		of_node_put(iommu_spec.np);
 	}