linux-kernel - Re: [Linux-kernel-mentees][PATCH v2] net: usb: rtl8150: prevent set_ethernet

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Date:   Sat, 03 Oct 2020 12:38:22 -0700
From:   Joe Perches <joe@...ches.com>
To:     Anant Thazhemadam <anant.thazhemadam@...il.com>
Cc:     linux-kernel-mentees@...ts.linuxfoundation.org,
        syzbot+abbc768b560c84d92fd3@...kaller.appspotmail.com,
        Petko Manolov <petkan@...leusys.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, linux-usb@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [Linux-kernel-mentees][PATCH v2] net: usb: rtl8150: prevent
 set_ethernet_addr from setting uninit address

On Thu, 2020-10-01 at 13:02 +0530, Anant Thazhemadam wrote:
> When get_registers() fails (which happens when usb_control_msg() fails)
> in set_ethernet_addr(), the uninitialized value of node_id gets copied
> as the address.

unrelated trivia:

> diff --git a/drivers/net/usb/rtl8150.c b/drivers/net/usb/rtl8150.c
[]
> @@ -274,12 +274,17 @@ static int write_mii_word(rtl8150_t * dev, u8 phy, __u8 indx, u16 reg)
>  		return 1;
>  }
>  
> -static inline void set_ethernet_addr(rtl8150_t * dev)
> +static bool set_ethernet_addr(rtl8150_t *dev)
>  {
>  	u8 node_id[6];

This might be better as:

	u8 node_id[ETH_ALEN];

> +	int ret;
>  
> -	get_registers(dev, IDR, sizeof(node_id), node_id);
> -	memcpy(dev->netdev->dev_addr, node_id, sizeof(node_id));
> +	ret = get_registers(dev, IDR, sizeof(node_id), node_id);
> +	if (ret == sizeof(node_id)) {
> +		memcpy(dev->netdev->dev_addr, node_id, sizeof(node_id));

and
		ether_addr_copy(dev->netdev->dev_addr, node_id);