iommu/dma: Fix for dereferencing before null checking

The cookie is dereferenced before null checking in the function
iommu_dma_init_domain.

This patch moves the dereferencing after the null checking.

Fixes: fdbe574eb6 ("iommu/dma: Allow MSI-only cookies")
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/dma-iommu.c

@@ -303,13 +303,15 @@ static int iommu_dma_init_domain(struct iommu_domain *domain, dma_addr_t base,
 		u64 size, struct device *dev)
 {
 	struct iommu_dma_cookie *cookie = domain->iova_cookie;
-	struct iova_domain *iovad = &cookie->iovad;
 	unsigned long order, base_pfn;
+	struct iova_domain *iovad;
 	int attr;
 
 	if (!cookie || cookie->type != IOMMU_DMA_IOVA_COOKIE)
 		return -EINVAL;
 
+	iovad = &cookie->iovad;
+
 	/* Use the smallest supported page size for IOVA granularity */
 	order = __ffs(domain->pgsize_bitmap);
 	base_pfn = max_t(unsigned long, 1, base >> order);