[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 <redacted>
Signed-off-by: Xin Tan <redacted>
---
 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


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

On 2021-06-09 14:35, Xiyu Yang wrote:

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.

If only there was some kind of helper function which could encapsulate 
the correct expected behaviour in a single place...

In fact with the new pm_runtime_resume_and_get() API I think these two 
patches boil down to a one-line change.

Thanks,
Robin.

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Thanks for your advice, I'll send a v2 patch soon.

-----Original Messages-----
From: "Robin Murphy" <robin.murphy@arm.com>
Sent Time: 2021-06-09 22:12:11 (Wednesday)
To: "Xiyu Yang" <redacted>, "Will Deacon" <will@kernel.org>, "Joerg Roedel" <joro@8bytes.org>, "Nicolin Chen" <nicoleotsuka@gmail.com>, "Bjorn Andersson" <redacted>, "Krishna Reddy" <vdumpa@nvidia.com>, "Jordan Crouse" <redacted>, "Sai Prakash Ranjan" <redacted>, linux-arm-kernel@lists.infradead.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Cc: yuanxzhang@fudan.edu.cn, "Xin Tan" <redacted>
Subject: Re: [PATCH] iommu/arm-smmu: Fix arm_smmu_device refcount leak when arm_smmu_rpm_get fails

On 2021-06-09 14:35, Xiyu Yang wrote:

quoted

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.

If only there was some kind of helper function which could encapsulate 
the correct expected behaviour in a single place...

In fact with the new pm_runtime_resume_and_get() API I think these two 
patches boil down to a one-line change.

Thanks,
Robin.

quoted

Signed-off-by: Xiyu Yang <redacted>
Signed-off-by: Xin Tan <redacted>
---
  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);
  

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel