linux-kernel - RE: [PATCH 5/7] staging: comedi: don't allow write() on async command set up for "read"

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Message-ID: <DC148C5AA1CEBA4E87973D432B1C2D882600D3B7@P3PWEX4MB008.ex4.secureserver.net>
Date:	Thu, 30 Oct 2014 18:07:43 +0000
From:	Hartley Sweeten <HartleyS@...ionengravers.com>
To:	Ian Abbott <abbotti@....co.uk>,
	"driverdev-devel@...uxdriverproject.org" 
	<driverdev-devel@...uxdriverproject.org>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 5/7] staging: comedi: don't allow write() on async
 command set up for "read"

On Thursday, October 30, 2014 5:43 AM, Ian Abbott wrote:
> If a Comedi asynchronous command has been set up for data transfer in
> the "read" direction on the current "write" subdevice (for those
> subdevices that support both directions), don't allow the "write" file
> operation as that would mess with the data in the comedi data buffer
> that is written by the low-level comedi hardware driver.
>
> Signed-off-by: Ian Abbott <abbotti@....co.uk>
> ---
>  drivers/staging/comedi/comedi_fops.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
> index 6805ec9..6328965 100644
> --- a/drivers/staging/comedi/comedi_fops.c
> +++ b/drivers/staging/comedi/comedi_fops.c
> @@ -2075,6 +2075,10 @@ static ssize_t comedi_write(struct file *file, const char __user *buf,
>  		retval = -EACCES;
>  		goto out;
>  	}
> +	if (!(async->cmd.flags & CMDF_WRITE)) {
> +		retval = -EINVAL;
> +		goto out;
> +	}
>  
>  	add_wait_queue(&async->wait_head, &wait);
>  	on_wait_queue = true;
> @@ -2146,6 +2150,10 @@ static ssize_t comedi_write(struct file *file, const char __user *buf,
>  				retval = -EACCES;
>  				break;
>  			}
> +			if (!(async->cmd.flags & CMDF_WRITE)) {
> +				retval = -EINVAL;
> +				break;
> +			}

Same question as with PATCH 4/7.

Is this test needed in the while () loop. Also, are the s->busy tests needed here?

>  			continue;
>  		}

Regards,
Hartley

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