netdev - Re: [net-next 07/14] ixgbe: eliminate Smatch warnings in ixgbe

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Message-ID: <20121026124122.GJ20754@mwanda>
Date:	Fri, 26 Oct 2012 15:41:22 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Cc:	davem@...emloft.net,
	"joshua.a.hay@...el.com" <joshua.a.hay@...el.com>,
	netdev@...r.kernel.org, gospo@...hat.com, sassmann@...hat.com
Subject: Re: [net-next 07/14] ixgbe: eliminate Smatch warnings in
 ixgbe_debugfs.c

On Fri, Oct 26, 2012 at 04:58:15AM -0700, Jeff Kirsher wrote:
> From: "joshua.a.hay@...el.com" <joshua.a.hay@...el.com>
> 
> This patch replaces calls to copy_to_user, copy_from_user, and the associated
> logic, with calls to simple_read_from_buffer and simple_write_to_buffer
> respectively.  This was done to eliminate warnings generated by the Smatch
> static analysis tool.

There were some bugs, it wasn't just about silencing warnings.

> +	buf = kasprintf(GFP_KERNEL, "%s: %s\n",
> +			adapter->netdev->name,
> +			ixgbe_dbg_reg_ops_buf);
> +	if (!buf)
> +		return -ENOMEM;
> +
> +	if (count < strlen(buf))
>  		return -ENOSPC;

You need a kfree(buf) here.

> -	ixgbe_dbg_reg_ops_buf[count] = '\0';
> +	len = simple_write_to_buffer(ixgbe_dbg_reg_ops_buf,
> +				     sizeof(ixgbe_dbg_reg_ops_buf),

This should be "sizeof(ixgbe_dbg_reg_ops_buf) - 1" to leave space
for the NUL terminator.

> +				     ppos,
> +				     buffer,
> +				     count);
> +	ixgbe_dbg_reg_ops_buf[len] = '\0';

simple_write_to_buffer() returns negative error codes so this could
corrupt memory.


> +	buf = kasprintf(GFP_KERNEL, "%s: %s\n",
> +			adapter->netdev->name,
> +			ixgbe_dbg_netdev_ops_buf);
> +	if (!buf)
> +		return -ENOMEM;
>  
> -	*ppos = len;
> +	if (count < strlen(buf))
> +		return -ENOSPC;

Missing kfree().

> -	ixgbe_dbg_netdev_ops_buf[count] = '\0';
> +	len = simple_write_to_buffer(ixgbe_dbg_netdev_ops_buf,
> +				     sizeof(ixgbe_dbg_netdev_ops_buf),
> +				     ppos,
> +				     buffer,
> +				     count);
> +	ixgbe_dbg_netdev_ops_buf[len] = '\0';

Same issues as before.

regards,
dan carpenter

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