netdev - Re: [PATCH net-next] ethtool: fix a memory leak in ethnl_default

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Date:   Wed, 8 Jan 2020 10:06:45 +0100
From:   Michal Kubecek <mkubecek@...e.cz>
To:     netdev@...r.kernel.org
Cc:     Dan Carpenter <dan.carpenter@...cle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH net-next] ethtool: fix a memory leak in
 ethnl_default_start()

On Wed, Jan 08, 2020 at 08:39:48AM +0300, Dan Carpenter wrote:
> If ethnl_default_parse() fails then we need to free a couple
> memory allocations before returning.
> 
> Fixes: 728480f12442 ("ethtool: default handlers for GET requests")
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> ---
>  net/ethtool/netlink.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
> index 4ca96c7b86b3..5d16436498ac 100644
> --- a/net/ethtool/netlink.c
> +++ b/net/ethtool/netlink.c
> @@ -472,8 +472,8 @@ static int ethnl_default_start(struct netlink_callback *cb)
>  		return -ENOMEM;
>  	reply_data = kmalloc(ops->reply_data_size, GFP_KERNEL);
>  	if (!reply_data) {
> -		kfree(req_info);
> -		return -ENOMEM;
> +		ret = -ENOMEM;
> +		goto free_req_info;
>  	}

We could avoid the block statement by setting ret unconditionally but
this is OK.
>  
>  	ret = ethnl_default_parse(req_info, cb->nlh, sock_net(cb->skb->sk), ops,
> @@ -487,7 +487,7 @@ static int ethnl_default_start(struct netlink_callback *cb)
>  		req_info->dev = NULL;
>  	}
>  	if (ret < 0)
> -		return ret;
> +		goto free_reply_data;
>  
>  	ctx->ops = ops;
>  	ctx->req_info = req_info;
> @@ -496,6 +496,13 @@ static int ethnl_default_start(struct netlink_callback *cb)
>  	ctx->pos_idx = 0;
>  
>  	return 0;
> +
> +free_reply_data:
> +	kfree(reply_data);
> +free_req_info:
> +	kfree(req_info);
> +
> +	return ret;
>  }
>  
>  /* default ->done() handler for GET requests */

Reviewed-by: Michal Kubecek <mkubecek@...e.cz>