[PATCH] iommu/msm: add a check for the return of kzalloc()

[PATCH] iommu/msm: add a check for the return of kzalloc()

[xkernel.wang]

From: Xiaoke Wang <xkernel.wang@foxmail.com>

kzalloc() is a memory allocation function which can return NULL when
some internal memory errors happen. So it is better to check it to
prevent potential wrong memory access.

Signed-off-by: Xiaoke Wang <xkernel.wang@foxmail.com>
---
 drivers/iommu/msm_iommu.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/iommu/msm_iommu.c b/drivers/iommu/msm_iommu.c
index 3a38352..697ad63 100644
--- a/drivers/iommu/msm_iommu.c
+++ b/drivers/iommu/msm_iommu.c
@@ -597,6 +597,10 @@ static void insert_iommu_master(struct device *dev,
 
 	if (list_empty(&(*iommu)->ctx_list)) {
 		master = kzalloc(sizeof(*master), GFP_ATOMIC);
+		if (!master) {
+			dev_err(dev, "Failed to allocate iommu_master\n");
+			return;
+		}
 		master->of_node = dev->of_node;
 		list_add(&master->list, &(*iommu)->ctx_list);
 		dev_iommu_priv_set(dev, master);
-- 

Re: [PATCH] iommu/msm: add a check for the return of kzalloc()

[Joerg Roedel]

On Fri, Mar 25, 2022 at 10:08:01AM +0800, xkernel.wang@foxmail.com wrote:
> From: Xiaoke Wang <xkernel.wang@foxmail.com>
> 
> kzalloc() is a memory allocation function which can return NULL when
> some internal memory errors happen. So it is better to check it to
> prevent potential wrong memory access.
> 
> Signed-off-by: Xiaoke Wang <xkernel.wang@foxmail.com>
> ---
>  drivers/iommu/msm_iommu.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/iommu/msm_iommu.c b/drivers/iommu/msm_iommu.c
> index 3a38352..697ad63 100644
> --- a/drivers/iommu/msm_iommu.c
> +++ b/drivers/iommu/msm_iommu.c
> @@ -597,6 +597,10 @@ static void insert_iommu_master(struct device *dev,
>  
>  	if (list_empty(&(*iommu)->ctx_list)) {
>  		master = kzalloc(sizeof(*master), GFP_ATOMIC);
> +		if (!master) {
> +			dev_err(dev, "Failed to allocate iommu_master\n");
> +			return;
> +		}

This is not enough, if the error happens it also need to be propagated
to the caller.

Regards,

	Joerg

Re: [PATCH] iommu/msm: add a check for the return of kzalloc()

[Jeffrey Hugo]

On Fri, Mar 25, 2022 at 2:13 PM <xkernel.wang@foxmail.com> wrote:
>
> From: Xiaoke Wang <xkernel.wang@foxmail.com>
>
> kzalloc() is a memory allocation function which can return NULL when
> some internal memory errors happen. So it is better to check it to
> prevent potential wrong memory access.
>
> Signed-off-by: Xiaoke Wang <xkernel.wang@foxmail.com>
> ---
>  drivers/iommu/msm_iommu.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/iommu/msm_iommu.c b/drivers/iommu/msm_iommu.c
> index 3a38352..697ad63 100644
> --- a/drivers/iommu/msm_iommu.c
> +++ b/drivers/iommu/msm_iommu.c
> @@ -597,6 +597,10 @@ static void insert_iommu_master(struct device *dev,
>
>         if (list_empty(&(*iommu)->ctx_list)) {
>                 master = kzalloc(sizeof(*master), GFP_ATOMIC);
> +               if (!master) {
> +                       dev_err(dev, "Failed to allocate iommu_master\n");

How do you reconcile this with chapter 14 of the coding style document?

"These generic allocation functions all emit a stack dump on failure when used
without __GFP_NOWARN so there is no use in emitting an additional failure
message when NULL is returned."

> +                       return;
> +               }
>                 master->of_node = dev->of_node;
>                 list_add(&master->list, &(*iommu)->ctx_list);
>                 dev_iommu_priv_set(dev, master);
> --