netdev - RE: [net-next 06/10] ixgbe: eliminate Smatch warnings in ixgbe

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Message-ID: <4329753313F5A742A09953EE6CC1B3CE28C7D984@ORSMSX108.amr.corp.intel.com>
Date:	Tue, 27 Nov 2012 01:06:17 +0000
From:	"Hay, Joshua A" <joshua.a.hay@...el.com>
To:	Dan Carpenter <dan.carpenter@...cle.com>,
	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>
CC:	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"gospo@...hat.com" <gospo@...hat.com>,
	"sassmann@...hat.com" <sassmann@...hat.com>
Subject: RE: [net-next 06/10] ixgbe: eliminate Smatch warnings in
 ixgbe_debugfs.c

The return value will be changed to len to preserve error codes returned from simple_write_to_buffer.

However, changing the logic preceding this return breaks these functions.  If simple_write_to_buffer returns a positive value, other actions are performed with this value.  With this patch, the function will return immediately with that value instead.  This will effectively break the ixgbe_debugfs write operations.

So ultimately, the change should be: 
> +	len = simple_write_to_buffer(ixgbe_dbg_reg_ops_buf,
> +				     sizeof(ixgbe_dbg_reg_ops_buf)-1,
> +				     ppos,
> +				     buffer,
> +				     count);
> +	if (len < 0)
> +		return -EFAULT;
	
	if (len < 0)
		return len;

Thanks,
Josh Hay

-----Original Message-----
From: Dan Carpenter [mailto:dan.carpenter@...cle.com] 
Sent: Wednesday, November 21, 2012 3:04 AM
To: Kirsher, Jeffrey T
Cc: davem@...emloft.net; Hay, Joshua A; netdev@...r.kernel.org; gospo@...hat.com; sassmann@...hat.com
Subject: Re: [net-next 06/10] ixgbe: eliminate Smatch warnings in ixgbe_debugfs.c

On Wed, Nov 21, 2012 at 02:47:32AM -0800, Jeff Kirsher wrote:
> +	len = simple_write_to_buffer(ixgbe_dbg_reg_ops_buf,
> +				     sizeof(ixgbe_dbg_reg_ops_buf)-1,
> +				     ppos,
> +				     buffer,
> +				     count);
> +	if (len < 0)
> +		return -EFAULT;

Any negative return is bad.

	if (len)
		return len;

> +
> +	ixgbe_dbg_reg_ops_buf[len] = '\0';
>  
>  	if (strncmp(ixgbe_dbg_reg_ops_buf, "write", 5) == 0) {
>  		u32 reg, value;
> @@ -187,15 +196,15 @@ static ssize_t ixgbe_dbg_netdev_ops_write(struct file *filp,
>  	if (count >= sizeof(ixgbe_dbg_netdev_ops_buf))
>  		return -ENOSPC;
>  
> -	bytes_not_copied = copy_from_user(ixgbe_dbg_netdev_ops_buf,
> -					  buffer, count);
> -	if (bytes_not_copied < 0)
> -		return bytes_not_copied;
> -	else if (bytes_not_copied < count)
> -		count -= bytes_not_copied;
> -	else
> -		return -ENOSPC;
> -	ixgbe_dbg_netdev_ops_buf[count] = '\0';
> +	len = simple_write_to_buffer(ixgbe_dbg_netdev_ops_buf,
> +				     sizeof(ixgbe_dbg_netdev_ops_buf)-1,
> +				     ppos,
> +				     buffer,
> +				     count);
> +	if (len < 0)
> +		return -EFAULT;

Same.

> +
> +	ixgbe_dbg_netdev_ops_buf[len] = '\0';

regards,
dan carpenter

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