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

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Date:   Fri, 10 Feb 2023 16:21:37 +0800
From:   Xu Yilun <yilun.xu@...el.com>
To:     k1rh4.lee@...il.com
Cc:     Wu Hao <hao.wu@...el.com>, Tom Rix <trix@...hat.com>,
        Moritz Fischer <mdf@...nel.org>, linux-fpga@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fpga: dfl-afu-region: Add overflow checks for region
 size and offset

On 2023-02-05 at 21:43:26 -0800, k1rh4.lee@...il.com wrote:
> From: Sangsup Lee <k1rh4.lee@...il.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@...il.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
>