Re: [PATCH] iommu: fix an incorrect NULL check on list iterator

[Joerg Roedel]

On Sun, Mar 27, 2022 at 01:35:58PM +0800, Xiaomeng Tong wrote:
> @@ -617,23 +617,17 @@ static int qcom_iommu_of_xlate(struct device *dev,
>  {
>   struct msm_iommu_dev *iommu;
>   unsigned long flags;
> - int ret = 0;
>  
>   spin_lock_irqsave(_iommu_lock, flags);
>   list_for_each_entry(iommu, _iommu_devices, dev_node)
> - if (iommu->dev->of_node == spec->np)
> - break;
> -
> - if (!iommu || iommu->dev->of_node != spec->np) {
> - ret = -ENODEV;
> - goto fail;
> - }
> -
> - insert_iommu_master(dev, , spec);
> -fail:
> + if (iommu->dev->of_node == spec->np) {
> + insert_iommu_master(dev, , spec);
> + spin_unlock_irqrestore(_iommu_lock, flags);
> + return 0;
> + }
>   spin_unlock_irqrestore(_iommu_lock, flags);
>  
> - return ret;
> + return -ENODEV;

This looks a bit clumsy, a better fix is below:

diff --git a/drivers/iommu/msm_iommu.c b/drivers/iommu/msm_iommu.c
index 50f57624610f..98d23c52537b 100644
--- a/drivers/iommu/msm_iommu.c
+++ b/drivers/iommu/msm_iommu.c
@@ -610,14 +610,16 @@ static void insert_iommu_master(struct device *dev,
 static int qcom_iommu_of_xlate(struct device *dev,
   struct of_phandle_args *spec)
 {
-   struct msm_iommu_dev *iommu;
+   struct msm_iommu_dev *iommu = NULL, *it;
unsigned long flags;
int ret = 0;
 
spin_lock_irqsave(_iommu_lock, flags);
-   list_for_each_entry(iommu, _iommu_devices, dev_node)
-   if (iommu->dev->of_node == spec->np)
+   list_for_each_entry(it, _iommu_devices, dev_node)
+   if (it->dev->of_node == spec->np) {
+   iommu = it;
break;
+   }
 
if (!iommu || iommu->dev->of_node != spec->np) {
ret = -ENODEV;

Can you please verify this and re-submit?

Thanks,

Joerg
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[RESEND][PATCH] iommu: fix an incorrect NULL check on list iterator

[Xiaomeng Tong]

The bug is here:
if (!iommu || iommu->dev->of_node != spec->np) {

The list iterator value 'iommu' will *always* be set and non-NULL by
list_for_each_entry(), so it is incorrect to assume that the iterator
value will be NULL if the list is empty or no element is found (in fact,
it will point to a invalid structure object containing HEAD).

To fix the bug, run insert_iommu_master(dev, , spec); unlock and
return 0 when found, otherwise unlock and return -ENODEV.

Cc: sta...@vger.kernel.org
Fixes: f78ebca8ff3d6 ("iommu/msm: Add support for generic master bindings")
Signed-off-by: Xiaomeng Tong 
---
 drivers/iommu/msm_iommu.c | 18 ++
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/drivers/iommu/msm_iommu.c b/drivers/iommu/msm_iommu.c
index 3a38352b603f..1dbb8b0695ec 100644
--- a/drivers/iommu/msm_iommu.c
+++ b/drivers/iommu/msm_iommu.c
@@ -617,23 +617,17 @@ static int qcom_iommu_of_xlate(struct device *dev,
 {
struct msm_iommu_dev *iommu;
unsigned long flags;
-   int ret = 0;
 
spin_lock_irqsave(_iommu_lock, flags);
list_for_each_entry(iommu, _iommu_devices, dev_node)
-   if (iommu->dev->of_node == spec->np)
-   break;
-
-   if (!iommu || iommu->dev->of_node != spec->np) {
-   ret = -ENODEV;
-   goto fail;
-   }
-
-   insert_iommu_master(dev, , spec);
-fail:
+   if (iommu->dev->of_node == spec->np) {
+   insert_iommu_master(dev, , spec);
+   spin_unlock_irqrestore(_iommu_lock, flags);
+   return 0;
+   }
spin_unlock_irqrestore(_iommu_lock, flags);
 
-   return ret;
+   return -ENODEV;
 }
 
 irqreturn_t msm_iommu_fault_handler(int irq, void *dev_id)
-- 
2.17.1

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[PATCH] iommu: fix an incorrect NULL check on list iterator

[Xiaomeng Tong]

The bug is here:
if (!iommu || iommu->dev->of_node != spec->np) {

The list iterator value 'iommu' will *always* be set and non-NULL by
list_for_each_entry(), so it is incorrect to assume that the iterator
value will be NULL if the list is empty or no element is found (in fact,
it will point to a invalid structure object containing HEAD).

To fix the bug, run insert_iommu_master(dev, , spec); unlock and
return 0 when found, otherwise unlock and return -ENODEV.

Cc: sta...@vger.kernel.org
Fixes: f78ebca8ff3d6 ("iommu/msm: Add support for generic master bindings")
Signed-off-by: Xiaomeng Tong 
---
 drivers/iommu/msm_iommu.c | 18 ++
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/drivers/iommu/msm_iommu.c b/drivers/iommu/msm_iommu.c
index 3a38352b603f..1dbb8b0695ec 100644
--- a/drivers/iommu/msm_iommu.c
+++ b/drivers/iommu/msm_iommu.c
@@ -617,23 +617,17 @@ static int qcom_iommu_of_xlate(struct device *dev,
 {
struct msm_iommu_dev *iommu;
unsigned long flags;
-   int ret = 0;
 
spin_lock_irqsave(_iommu_lock, flags);
list_for_each_entry(iommu, _iommu_devices, dev_node)
-   if (iommu->dev->of_node == spec->np)
-   break;
-
-   if (!iommu || iommu->dev->of_node != spec->np) {
-   ret = -ENODEV;
-   goto fail;
-   }
-
-   insert_iommu_master(dev, , spec);
-fail:
+   if (iommu->dev->of_node == spec->np) {
+   insert_iommu_master(dev, , spec);
+   spin_unlock_irqrestore(_iommu_lock, flags);
+   return 0;
+   }
spin_unlock_irqrestore(_iommu_lock, flags);
 
-   return ret;
+   return -ENODEV;
 }
 
 irqreturn_t msm_iommu_fault_handler(int irq, void *dev_id)
-- 
2.17.1

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