2022-12-23 07:59:02

by Li kunyu

Subject: [PATCH] vfio_iommu_type1: increase the validity check of function parameters

Added validity check for count variable, return if count variable does
not meet the execution condition (do not execute mutex_lock and
mutex_unlock function).

Signed-off-by: Li kunyu <[email protected]>
---
drivers/vfio/vfio_iommu_type1.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 23c24fe98c00..9bdf96d932e4 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -3137,6 +3137,9 @@ static int vfio_iommu_type1_dma_rw(void *iommu_data, dma_addr_t user_iova,
int ret = 0;
size_t done;

+ if (count <= 0)
+ return ret;
+
mutex_lock(&iommu->lock);
while (count > 0) {
ret = vfio_iommu_type1_dma_rw_chunk(iommu, user_iova, data,
--
2.18.2

2022-12-23 13:55:24

by Alex Williamson

Subject: Re: [PATCH] vfio_iommu_type1: increase the validity check of function parameters

On Fri, 23 Dec 2022 15:24:18 +0800
Li kunyu <[email protected]> wrote:

> Added validity check for count variable, return if count variable does
> not meet the execution condition (do not execute mutex_lock and
> mutex_unlock function).
>
> Signed-off-by: Li kunyu <[email protected]>
> ---
> drivers/vfio/vfio_iommu_type1.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 23c24fe98c00..9bdf96d932e4 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -3137,6 +3137,9 @@ static int vfio_iommu_type1_dma_rw(void *iommu_data, dma_addr_t user_iova,
> int ret = 0;
> size_t done;
>
> + if (count <= 0)
> + return ret;
> +
> mutex_lock(&iommu->lock);
> while (count > 0) {
> ret = vfio_iommu_type1_dma_rw_chunk(iommu, user_iova, data,

This is only optimizing a case that shouldn't exist, the return value
is the same. Callers should be smart enough not to call the function
with such values. As an internal API, we assume reasonable behavior by
the caller. Thanks,

Alex