linux-kernel - Re: [PATCH AUTOSEL 5.8 18/24] net: usb: rtl8150: set random MAC address when set_ethernet

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Message-ID: <c93d120c850c5fecadaea845517f0fdbfd9a61c7.camel@perches.com>
Date:   Mon, 12 Oct 2020 12:11:18 -0700
From:   Joe Perches <joe@...ches.com>
To:     Sasha Levin <sashal@...nel.org>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Cc:     Anant Thazhemadam <anant.thazhemadam@...il.com>,
        syzbot+abbc768b560c84d92fd3@...kaller.appspotmail.com,
        Petko Manolov <petkan@...leusys.com>,
        "David S . Miller" <davem@...emloft.net>,
        linux-usb@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH AUTOSEL 5.8 18/24] net: usb: rtl8150: set random MAC
 address when set_ethernet_addr() fails

On Mon, 2020-10-12 at 15:02 -0400, Sasha Levin wrote:
> From: Anant Thazhemadam <anant.thazhemadam@...il.com>
> 
> [ Upstream commit f45a4248ea4cc13ed50618ff066849f9587226b2 ]
> 
> When get_registers() fails in set_ethernet_addr(),the uninitialized
> value of node_id gets copied over as the address.
> So, check the return value of get_registers().
> 
> If get_registers() executed successfully (i.e., it returns
> sizeof(node_id)), copy over the MAC address using ether_addr_copy()
> (instead of using memcpy()).
> 
> Else, if get_registers() failed instead, a randomly generated MAC
> address is set as the MAC address instead.

This autosel is premature.

This patch always sets a random MAC.
See the follow on patch: https://lkml.org/lkml/2020/10/11/131
To my knowledge, this follow-ob has yet to be applied:

> diff --git a/drivers/net/usb/rtl8150.c b/drivers/net/usb/rtl8150.c
[]
> @@ -274,12 +274,20 @@ 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 void set_ethernet_addr(rtl8150_t *dev)
>  {
> -	u8 node_id[6];
> +	u8 node_id[ETH_ALEN];
> +	int ret;
> +
> +	ret = get_registers(dev, IDR, sizeof(node_id), node_id);
>  
> -	get_registers(dev, IDR, sizeof(node_id), node_id);
> -	memcpy(dev->netdev->dev_addr, node_id, sizeof(node_id));
> +	if (ret == sizeof(node_id)) {

So this needs to use
	if (!ret) {

or 
	if (ret < 0)

and reversed code blocks

> +		ether_addr_copy(dev->netdev->dev_addr, node_id);
> +	} else {
> +		eth_hw_addr_random(dev->netdev);
> +		netdev_notice(dev->netdev, "Assigned a random MAC address: %pM\n",
> +			      dev->netdev->dev_addr);
> +	}
>  }
>  
>  static int rtl8150_set_mac_address(struct net_device *netdev, void *p)