linux-kernel - Re: [PATCH] appletouch: fix DMA to/from stack buffer

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Date:	Tue, 28 Apr 2009 10:44:54 +0200
From:	Johannes Berg <johannes@...solutions.net>
To:	Bob Copeland <me@...copeland.com>
Cc:	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] appletouch: fix DMA to/from stack buffer

On Mon, 2009-04-27 at 21:58 -0400, Bob Copeland wrote:
> CONFIG_DMA_API_DEBUG spotted an instance of appletouch using
> an array on the stack as a DMA buffer for certain hardware.
> Change it to use a kmalloc()ed buffer instead.
> 
> This fixes the following error:

> Signed-off-by: Bob Copeland <me@...copeland.com>

Reviewed-by: Johannes Berg <johannes@...solutions.net>

Interestingly, I first thought the GFP_KERNEL is wrong due to
atp_reinit, but the GFP_ATOMIC in that is wrong instead :)

> ---
>  drivers/input/mouse/appletouch.c |   24 ++++++++++++++++++------
>  1 files changed, 18 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/input/mouse/appletouch.c b/drivers/input/mouse/appletouch.c
> index 454b961..e0140fd 100644
> --- a/drivers/input/mouse/appletouch.c
> +++ b/drivers/input/mouse/appletouch.c
> @@ -255,15 +255,22 @@ MODULE_PARM_DESC(debug, "Activate debugging output");
>   */
>  static int atp_geyser_init(struct usb_device *udev)
>  {
> -	char data[8];
> +	char *data;
>  	int size;
>  	int i;
> +	int ret;
> +
> +	data = kmalloc(8, GFP_KERNEL);
> +	if (!data) {
> +		err("Out of memory");
> +		return -ENOMEM;
> +	}
>  
>  	size = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0),
>  			ATP_GEYSER_MODE_READ_REQUEST_ID,
>  			USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE,
>  			ATP_GEYSER_MODE_REQUEST_VALUE,
> -			ATP_GEYSER_MODE_REQUEST_INDEX, &data, 8, 5000);
> +			ATP_GEYSER_MODE_REQUEST_INDEX, data, 8, 5000);
>  
>  	if (size != 8) {
>  		dprintk("atp_geyser_init: read error\n");
> @@ -271,7 +278,8 @@ static int atp_geyser_init(struct usb_device *udev)
>  			dprintk("appletouch[%d]: %d\n", i, data[i]);
>  
>  		err("Failed to read mode from device.");
> -		return -EIO;
> +		ret = -EIO;
> +		goto out_free;
>  	}
>  
>  	/* Apply the mode switch */
> @@ -281,7 +289,7 @@ static int atp_geyser_init(struct usb_device *udev)
>  			ATP_GEYSER_MODE_WRITE_REQUEST_ID,
>  			USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE,
>  			ATP_GEYSER_MODE_REQUEST_VALUE,
> -			ATP_GEYSER_MODE_REQUEST_INDEX, &data, 8, 5000);
> +			ATP_GEYSER_MODE_REQUEST_INDEX, data, 8, 5000);
>  
>  	if (size != 8) {
>  		dprintk("atp_geyser_init: write error\n");
> @@ -289,9 +297,13 @@ static int atp_geyser_init(struct usb_device *udev)
>  			dprintk("appletouch[%d]: %d\n", i, data[i]);
>  
>  		err("Failed to request geyser raw mode");
> -		return -EIO;
> +		ret = -EIO;
> +		goto out_free;
>  	}
> -	return 0;
> +	ret = 0;
> +out_free:
> +	kfree(data);
> +	return ret;
>  }
>  
>  /*
> -- 
> 1.6.0.6
> 

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