linux-kernel - Re: [PATCH 1/1] comedi: ni_usb6501: fix transfer-buffer overflows

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Date:   Mon, 6 Jun 2022 11:03:28 +0100
From:   Ian Abbott <abbotti@....co.uk>
To:     Xiaohui Zhang <ruc_zhangxiaohui@....com>,
        H Hartley Sweeten <hsweeten@...ionengravers.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Johan Hovold <johan@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] comedi: ni_usb6501: fix transfer-buffer overflows

On 05/06/2022 13:43, Xiaohui Zhang wrote:
> From: xiaohuizhang98 <ruc_zhangxiaohui@....com>
> 
> We detected a suspected bug with our code clone detection tool.
> 
> Similar to the handling of vmk80xx_alloc_usb_buffers in commit
> a23461c47482("comedi: vmk80xx: fix transfer-buffer overflows"),
> we thought a patch might be needed here as well.
> 
> The driver uses endpoint-sized USB transfer buffers but up until
> recently had no sanity checks on the sizes.
> 
> Signed-off-by: xiaohuizhang98 <ruc_zhangxiaohui@....com>
> ---
>   drivers/comedi/drivers/ni_usb6501.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/comedi/drivers/ni_usb6501.c b/drivers/comedi/drivers/ni_usb6501.c
> index 0dd9edf7bced..3e2b9f4d840b 100644
> --- a/drivers/comedi/drivers/ni_usb6501.c
> +++ b/drivers/comedi/drivers/ni_usb6501.c
> @@ -90,6 +90,7 @@
>   #include <linux/comedi/comedi_usb.h>
>   
>   #define	NI6501_TIMEOUT	1000
> +#define MIN_BUF_SIZE	64
>   
>   /* Port request packets */
>   static const u8 READ_PORT_REQUEST[]	= {0x00, 0x01, 0x00, 0x10,
> @@ -459,12 +460,12 @@ static int ni6501_alloc_usb_buffers(struct comedi_device *dev)
>   	struct ni6501_private *devpriv = dev->private;
>   	size_t size;
>   
> -	size = usb_endpoint_maxp(devpriv->ep_rx);
> +	size = max(usb_endpoint_maxp(devpriv->ep_rx), MIN_BUF_SIZE);
>   	devpriv->usb_rx_buf = kzalloc(size, GFP_KERNEL);
>   	if (!devpriv->usb_rx_buf)
>   		return -ENOMEM;
>   
> -	size = usb_endpoint_maxp(devpriv->ep_tx);
> +	size = max(usb_endpoint_maxp(devpriv->ep_rx), MIN_BUF_SIZE);
>   	devpriv->usb_tx_buf = kzalloc(size, GFP_KERNEL);
>   	if (!devpriv->usb_tx_buf)
>   		return -ENOMEM;

Actually, there is a typo in the last bit of the patch that was copied 
from the similar patch to vmk80xx.  It is using the wrong endpoint to 
determine the size for usb_tx_buf.

-- 
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