linux-kernel - [PATCH] iommu/dma: fix for dereferencing before null checking

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Message-ID: <1566611232-165399-1-git-send-email-linyunsheng@huawei.com>
Date:   Sat, 24 Aug 2019 09:47:12 +0800
From:   Yunsheng Lin <linyunsheng@...wei.com>
To:     <joro@...tes.org>
CC:     <iommu@...ts.linux-foundation.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] 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: fdbe574eb693 ("iommu/dma: Allow MSI-only cookies")
Signed-off-by: Yunsheng Lin <linyunsheng@...wei.com>
---
 drivers/iommu/dma-iommu.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index d991d40..cdf7814 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/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);
-- 
2.8.1