[PATCH] fpga: dfl-afu-region: Add overflow checks for region size and offset

[PATCH] fpga: dfl-afu-region: Add overflow checks for region size and offset

[k1rh4.lee]

From: Sangsup Lee <k1rh4.lee@gmail.com>

The size + offset is able to be integer overflow value and it lead to mis-allocate region.

Signed-off-by: Sangsup Lee <k1rh4.lee@gmail.com>
---
 drivers/fpga/dfl-afu-region.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/fpga/dfl-afu-region.c b/drivers/fpga/dfl-afu-region.c
index 2e7b41629406..82b530111601 100644
--- a/drivers/fpga/dfl-afu-region.c
+++ b/drivers/fpga/dfl-afu-region.c
@@ -151,12 +151,17 @@ int afu_mmio_region_get_by_offset(struct dfl_feature_platform_data *pdata,
 	struct dfl_afu_mmio_region *region;
 	struct dfl_afu *afu;
 	int ret = 0;
+	u64 region_size = 0;
 
 	mutex_lock(&pdata->lock);
+	if (check_add_overflow(offset, size, &region_size)) {
+		ret = -EINVAL;
+		goto exit;
+	}
 	afu = dfl_fpga_pdata_get_private(pdata);
 	for_each_region(region, afu)
 		if (region->offset <= offset &&
-		    region->offset + region->size >= offset + size) {
+		    region->offset + region->size >= region_size) {
 			*pregion = *region;
 			goto exit;
 		}
-- 
2.25.1

Re: [PATCH] fpga: dfl-afu-region: Add overflow checks for region size and offset

[Russ Weight]

On 2/5/23 21:43, k1rh4.lee@gmail.com wrote:
> From: Sangsup Lee <k1rh4.lee@gmail.com>
>
> The size + offset is able to be integer overflow value and it lead to mis-allocate region.
Reviewed-by: Russ Weight <russell.h.weight@intel.com>
> Signed-off-by: Sangsup Lee <k1rh4.lee@gmail.com>
> ---
>  drivers/fpga/dfl-afu-region.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/fpga/dfl-afu-region.c b/drivers/fpga/dfl-afu-region.c
> index 2e7b41629406..82b530111601 100644
> --- a/drivers/fpga/dfl-afu-region.c
> +++ b/drivers/fpga/dfl-afu-region.c
> @@ -151,12 +151,17 @@ int afu_mmio_region_get_by_offset(struct dfl_feature_platform_data *pdata,
>  	struct dfl_afu_mmio_region *region;
>  	struct dfl_afu *afu;
>  	int ret = 0;
> +	u64 region_size = 0;
>  
>  	mutex_lock(&pdata->lock);
> +	if (check_add_overflow(offset, size, &region_size)) {
> +		ret = -EINVAL;
> +		goto exit;
> +	}
>  	afu = dfl_fpga_pdata_get_private(pdata);
>  	for_each_region(region, afu)
>  		if (region->offset <= offset &&
> -		    region->offset + region->size >= offset + size) {
> +		    region->offset + region->size >= region_size) {
>  			*pregion = *region;
>  			goto exit;
>  		}

Re: [PATCH] fpga: dfl-afu-region: Add overflow checks for region size and offset

[Xu Yilun]

On 2023-02-05 at 21:43:26 -0800, k1rh4.lee@gmail.com wrote:
> From: Sangsup Lee <k1rh4.lee@gmail.com>
> 
> The size + offset is able to be integer overflow value and it lead to mis-allocate region.

But I didn't see the memory allocation.

> 
> Signed-off-by: Sangsup Lee <k1rh4.lee@gmail.com>
> ---
>  drivers/fpga/dfl-afu-region.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/fpga/dfl-afu-region.c b/drivers/fpga/dfl-afu-region.c
> index 2e7b41629406..82b530111601 100644
> --- a/drivers/fpga/dfl-afu-region.c
> +++ b/drivers/fpga/dfl-afu-region.c
> @@ -151,12 +151,17 @@ int afu_mmio_region_get_by_offset(struct dfl_feature_platform_data *pdata,
>  	struct dfl_afu_mmio_region *region;
>  	struct dfl_afu *afu;
>  	int ret = 0;
> +	u64 region_size = 0;

Reverse Xmax tree please.

>  
>  	mutex_lock(&pdata->lock);
> +	if (check_add_overflow(offset, size, &region_size)) {

I'm not sure if the check is necessary.

The offset comes from: offset = vma->vm_pgoff << PAGE_SHIFT
The size comes from: size = vma->vm_end - vma->vm_start
Is it possible the upper mm layer passes invalid vma?

Thanks,
Yilun

> +		ret = -EINVAL;
> +		goto exit;
> +	}
>  	afu = dfl_fpga_pdata_get_private(pdata);
>  	for_each_region(region, afu)
>  		if (region->offset <= offset &&
> -		    region->offset + region->size >= offset + size) {
> +		    region->offset + region->size >= region_size) {
>  			*pregion = *region;
>  			goto exit;
>  		}
> -- 
> 2.25.1
> 

Re: [PATCH] fpga: dfl-afu-region: Add overflow checks for region size and offset

[Salvatore Bonaccorso]

Hi,

On Fri, Feb 10, 2023 at 04:21:37PM +0800, Xu Yilun wrote:
> On 2023-02-05 at 21:43:26 -0800, k1rh4.lee@gmail.com wrote:
> > From: Sangsup Lee <k1rh4.lee@gmail.com>
> > 
> > The size + offset is able to be integer overflow value and it lead to mis-allocate region.
> 
> But I didn't see the memory allocation.
> 
> > 
> > Signed-off-by: Sangsup Lee <k1rh4.lee@gmail.com>
> > ---
> >  drivers/fpga/dfl-afu-region.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/fpga/dfl-afu-region.c b/drivers/fpga/dfl-afu-region.c
> > index 2e7b41629406..82b530111601 100644
> > --- a/drivers/fpga/dfl-afu-region.c
> > +++ b/drivers/fpga/dfl-afu-region.c
> > @@ -151,12 +151,17 @@ int afu_mmio_region_get_by_offset(struct dfl_feature_platform_data *pdata,
> >  	struct dfl_afu_mmio_region *region;
> >  	struct dfl_afu *afu;
> >  	int ret = 0;
> > +	u64 region_size = 0;
> 
> Reverse Xmax tree please.
> 
> >  
> >  	mutex_lock(&pdata->lock);
> > +	if (check_add_overflow(offset, size, &region_size)) {
> 
> I'm not sure if the check is necessary.
> 
> The offset comes from: offset = vma->vm_pgoff << PAGE_SHIFT
> The size comes from: size = vma->vm_end - vma->vm_start
> Is it possible the upper mm layer passes invalid vma?
> 
> Thanks,
> Yilun

Did you saw the comments on your patch by Yilun? Did it felt trough
the cracks?

Regards,
Salvatore

Re: [PATCH] fpga: dfl-afu-region: Add overflow checks for region size and offset

[sangsup lee]

Hi,

In my opinion the code has an insecure code pattern.
The size may have integer overflow condition i think.
But, I did  not do dynamic analysis but I did static audit fpga code(I
don't have an fpga device).
because of this.  I don't make sure about Yilun's comment.
I think the code must have defensive coding rules.

best regards.