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

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Date:   Wed,  9 Jun 2021 21:35:07 +0800
From:   Xiyu Yang <xiyuyang19@...an.edu.cn>
To:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        Nicolin Chen <nicoleotsuka@...il.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Krishna Reddy <vdumpa@...dia.com>,
        Jordan Crouse <jordan@...micpenguin.net>,
        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 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 arm_smmu_rpm_put() or jumping to the "rpm_put"
label when arm_smmu_rpm_get() fails.

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 | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
index 6f72c4d208ca..177ee54c5534 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
@@ -840,7 +840,7 @@ static void arm_smmu_destroy_domain_context(struct iommu_domain *domain)
 
 	ret = arm_smmu_rpm_get(smmu);
 	if (ret < 0)
-		return;
+		goto rpm_put;
 
 	/*
 	 * Disable the context bank and free the page tables before freeing
@@ -857,6 +857,7 @@ static void arm_smmu_destroy_domain_context(struct iommu_domain *domain)
 	free_io_pgtable_ops(smmu_domain->pgtbl_ops);
 	__arm_smmu_free_bitmap(smmu->context_map, cfg->cbndx);
 
+rpm_put:
 	arm_smmu_rpm_put(smmu);
 }
 
@@ -1153,7 +1154,7 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
 
 	ret = arm_smmu_rpm_get(smmu);
 	if (ret < 0)
-		return ret;
+		goto rpm_put;
 
 	/* Ensure that the domain is finalised */
 	ret = arm_smmu_init_domain_context(domain, smmu, dev);
@@ -1404,7 +1405,7 @@ static struct iommu_device *arm_smmu_probe_device(struct device *dev)
 
 	ret = arm_smmu_rpm_get(smmu);
 	if (ret < 0)
-		goto out_cfg_free;
+		goto rpm_put;
 
 	ret = arm_smmu_master_alloc_smes(dev);
 	arm_smmu_rpm_put(smmu);
@@ -1417,6 +1418,8 @@ static struct iommu_device *arm_smmu_probe_device(struct device *dev)
 
 	return &smmu->iommu;
 
+rpm_put:
+	arm_smmu_rpm_put(smmu);
 out_cfg_free:
 	kfree(cfg);
 out_free:
@@ -1438,8 +1441,10 @@ static void arm_smmu_release_device(struct device *dev)
 	smmu = cfg->smmu;
 
 	ret = arm_smmu_rpm_get(smmu);
-	if (ret < 0)
+	if (ret < 0) {
+		arm_smmu_rpm_put(smmu);
 		return;
+	}
 
 	arm_smmu_master_free_smes(cfg, fwspec);
 
-- 
2.7.4