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

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Date:   Tue, 13 Oct 2020 00:01:06 +0300
From:   Petko Manolov <petkan@...leusys.com>
To:     Joe Perches <joe@...ches.com>
Cc:     Sasha Levin <sashal@...nel.org>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org,
        Anant Thazhemadam <anant.thazhemadam@...il.com>,
        syzbot+abbc768b560c84d92fd3@...kaller.appspotmail.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 20-10-12 12:11:18, Joe Perches wrote:
> 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:

ACK, the follow-on patch has got the correct semantics.


		Petko


> > 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)
> 
>