linux-kernel - [PATCH] iommu/arm-smmu: Fix arm_smmu_device refcount leak in address translation

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Date:   Wed,  9 Jun 2021 21:33:24 +0800
From:   Xiyu Yang <xiyuyang19@...an.edu.cn>
To:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Jordan Crouse <jordan@...micpenguin.net>,
        Krishna Reddy <vdumpa@...dia.com>,
        Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
        linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Cc:     yuanxzhang@...an.edu.cn, Xiyu Yang <xiyuyang19@...an.edu.cn>,
        Xin Tan <tanxin.ctf@...il.com>
Subject: [PATCH] iommu/arm-smmu: Fix arm_smmu_device refcount leak in address translation

arm_smmu_rpm_get() invokes pm_runtime_get_sync(), which increases the
refcount of the "smmu" even though the return value is less than 0.

The reference counting issue happens in several exception handling paths
of arm_smmu_iova_to_phys_hard(). When those error scenarios occur, the
function forgets to decrease the refcount of "smmu" increased by
arm_smmu_rpm_get(), causing a refcount leak.

Fix this issue by jumping to "out" label when those error scenarios
occur.

Signed-off-by: Xiyu Yang <xiyuyang19@...an.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@...il.com>
---
 drivers/iommu/arm/arm-smmu/arm-smmu.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
index 6f72c4d208ca..023dcd72ed35 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
@@ -1271,10 +1271,11 @@ static phys_addr_t arm_smmu_iova_to_phys_hard(struct iommu_domain *domain,
 	u64 phys;
 	unsigned long va, flags;
 	int ret, idx = cfg->cbndx;
+	phys_addr_t addr = 0;
 
 	ret = arm_smmu_rpm_get(smmu);
 	if (ret < 0)
-		return 0;
+		goto out;
 
 	spin_lock_irqsave(&smmu_domain->cb_lock, flags);
 	va = iova & ~0xfffUL;
@@ -1290,6 +1291,7 @@ static phys_addr_t arm_smmu_iova_to_phys_hard(struct iommu_domain *domain,
 		dev_err(dev,
 			"iova to phys timed out on %pad. Falling back to software table walk.\n",
 			&iova);
+		arm_smmu_rpm_put(smmu);
 		return ops->iova_to_phys(ops, iova);
 	}
 
@@ -1298,12 +1300,14 @@ static phys_addr_t arm_smmu_iova_to_phys_hard(struct iommu_domain *domain,
 	if (phys & ARM_SMMU_CB_PAR_F) {
 		dev_err(dev, "translation fault!\n");
 		dev_err(dev, "PAR = 0x%llx\n", phys);
-		return 0;
+		goto out;
 	}
 
+	addr = (phys & GENMASK_ULL(39, 12)) | (iova & 0xfff);
+out:
 	arm_smmu_rpm_put(smmu);
 
-	return (phys & GENMASK_ULL(39, 12)) | (iova & 0xfff);
+	return addr;
 }
 
 static phys_addr_t arm_smmu_iova_to_phys(struct iommu_domain *domain,
-- 
2.7.4