linux-kernel - [PATCH][next] iommu/vt-d: Fix dereference of pointer info before it is null checked

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Date:   Fri, 11 Jun 2021 14:50:24 +0100
From:   Colin King <colin.king@...onical.com>
To:     David Woodhouse <dwmw2@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        iommu@...ts.linux-foundation.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][next] iommu/vt-d: Fix dereference of pointer info before it is null checked

From: Colin Ian King <colin.king@...onical.com>

The assignment of iommu from info->iommu occurs before info is null checked
hence leading to a potential null pointer dereference issue. Fix this by
assigning iommu and checking if iommu is null after null checking info.

Addresses-Coverity: ("Dereference before null check")
Fixes: 4c82b88696ac ("iommu/vt-d: Allocate/register iopf queue for sva devices")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 drivers/iommu/intel/iommu.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index bd93c7ec879e..76a58b8ad6c3 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -5329,10 +5329,14 @@ static int intel_iommu_disable_auxd(struct device *dev)
 static int intel_iommu_enable_sva(struct device *dev)
 {
 	struct device_domain_info *info = get_domain_info(dev);
-	struct intel_iommu *iommu = info->iommu;
+	struct intel_iommu *iommu;
 	int ret;
 
-	if (!info || !iommu || dmar_disabled)
+	if (!info || dmar_disabled)
+		return -EINVAL;
+
+	iommu = info->iommu;
+	if (!iommu)
 		return -EINVAL;
 
 	if (!(iommu->flags & VTD_FLAG_SVM_CAPABLE))
-- 
2.31.1