linux-kernel - [PATCH v2] iommu/arm-smmu: Fix arm_smmu_device refcount leak when arm_smmu_rpm

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Message-Id: <1623293672-17954-1-git-send-email-xiyuyang19@fudan.edu.cn>
Date:   Thu, 10 Jun 2021 10:54:29 +0800
From:   Xiyu Yang <xiyuyang19@...an.edu.cn>
To:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        Jordan Crouse <jordan@...micpenguin.net>,
        Nicolin Chen <nicoleotsuka@...il.com>,
        Krishna Reddy <vdumpa@...dia.com>,
        Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
        Xiyu Yang <xiyuyang19@...an.edu.cn>,
        linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Cc:     yuanxzhang@...an.edu.cn, Xin Tan <tanxin.ctf@...il.com>
Subject: [PATCH v2] iommu/arm-smmu: Fix arm_smmu_device refcount leak when arm_smmu_rpm_get fails

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 some error handling paths of
arm_smmu_rpm_get() in its caller functions. When arm_smmu_rpm_get()
fails, the caller functions forget to decrease the refcount of "smmu"
increased by arm_smmu_rpm_get(), causing a refcount leak.

Fix this issue by calling pm_runtime_resume_and_get() instead of
pm_runtime_get_sync() in arm_smmu_rpm_get(), which can keep the refcount
balanced in case of failure.

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 | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
index 3a3847277320..1a647e0ea3eb 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
@@ -74,7 +74,7 @@ static bool using_legacy_binding, using_generic_binding;
 static inline int arm_smmu_rpm_get(struct arm_smmu_device *smmu)
 {
 	if (pm_runtime_enabled(smmu->dev))
-		return pm_runtime_get_sync(smmu->dev);
+		return pm_runtime_resume_and_get(smmu->dev);
 
 	return 0;
 }
-- 
2.7.4