netdev - Re: [PATCH 4/5] net: add support for nvmem to eth_platform_get_mac

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Message-ID: <20180718164218.GD12477@lunn.ch>
Date:   Wed, 18 Jul 2018 18:42:18 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Bartosz Golaszewski <brgl@...ev.pl>
Cc:     Sekhar Nori <nsekhar@...com>, Kevin Hilman <khilman@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Grygorii Strashko <grygorii.strashko@...com>,
        "David S . Miller" <davem@...emloft.net>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Lukas Wunner <lukas@...ner.de>, Rob Herring <robh@...nel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>,
        David Lechner <david@...hnology.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-omap@...r.kernel.org, netdev@...r.kernel.org,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH 4/5] net: add support for nvmem to
 eth_platform_get_mac_address()

> +		if (!IS_ERR(nvmem)) {
> +			addr = nvmem_cell_read(nvmem, &alen);
> +			if (!IS_ERR(addr)) {
> +				from = "nvmem";
> +				/* Don't use ether_addr_copy() in case we
> +				 * didn't get the right size.
> +				 */

Please verify the size. A short read can still give a valid MAC
address, so the is_valid_ether_addr(addr) is not sufficient.

> +				memcpy(addrbuf, addr, alen);

Another reason to check the length is that you appear to have a buffer
overflow here, if alen > 6.

	 Andrew

> +				kfree(addr);
> +				addr = addrbuf;
> +			}
> +
> +			nvmem_cell_put(nvmem);
> +		}
> +	}
> +
>  	if (!addr || !is_valid_ether_addr(addr))
>  		return -ENODEV;
>  
> -- 
> 2.17.1
>