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Date:   Mon, 9 May 2022 12:03:48 +0800
From:   Wang Cheng <wanngchenng@gmail.com>
To:     Pavel Skripkin <paskripkin@gmail.com>
Cc:     dan.carpenter@oracle.com, linux-staging@lists.linux.dev,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/2] staging: rtl8712: fix uninit-value in
 r871xu_drv_init()
Message-ID: <20220509040348.57f3nbudn2izodqw@ppc.localdomain>
References: <cover.1651760402.git.wanngchenng@gmail.com>
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 <46b89616-5ec7-fb04-f561-2647efd968c4@gmail.com>
 <20220506113320.gc6zryhm7uqnbva5@ppc.localdomain>
 <a5483e41-b5f7-d86b-21b9-2a9c3e602855@gmail.com>
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On 22/05/06 03:02PM, Pavel Skripkin wrote:
> Hi Wang,
> 
> On 5/6/22 14:33, Wang Cheng wrote:
> > On 22/05/06 10:41AM, Pavel Skripkin wrote:
> > > Hi Wang,
> > > 
> > > On 5/6/22 06:16, Wang Cheng wrote:
> > > 
> > > [snip]
> > > 
> > > > > Reported-and-tested-by:
> > > syzbot+6f5ecd144854c0d8580b@syzkaller.appspotmail.com
> > > > Signed-off-by: Wang Cheng <wanngchenng@gmail.com>
> > > > ---
> > > >   drivers/staging/rtl8712/usb_intf.c | 6 +++---
> > > >   1 file changed, 3 insertions(+), 3 deletions(-)
> > > > > diff --git a/drivers/staging/rtl8712/usb_intf.c
> > > b/drivers/staging/rtl8712/usb_intf.c
> > > > index ee4c61f85a07..50dcd3ecb685 100644
> > > > --- a/drivers/staging/rtl8712/usb_intf.c
> > > > +++ b/drivers/staging/rtl8712/usb_intf.c
> > > > @@ -538,13 +538,13 @@ static int r871xu_drv_init(struct usb_interface *pusb_intf,
> > > >   		} else {
> > > >   			AutoloadFail = false;
> > > >   		}
> > > > -		if (((mac[0] == 0xff) && (mac[1] == 0xff) &&
> > > > +		if ((!AutoloadFail) ||
> > > > +		    ((mac[0] == 0xff) && (mac[1] == 0xff) &&
> > > >   		     (mac[2] == 0xff) && (mac[3] == 0xff) &&
> > > >   		     (mac[4] == 0xff) && (mac[5] == 0xff)) ||
> > > >   		    ((mac[0] == 0x00) && (mac[1] == 0x00) &&
> > > >   		     (mac[2] == 0x00) && (mac[3] == 0x00) &&
> > > > -		     (mac[4] == 0x00) && (mac[5] == 0x00)) ||
> > > > -		     (!AutoloadFail)) {
> > > > +		     (mac[4] == 0x00) && (mac[5] == 0x00))) {
> > > 
> > > 
> > > That looks ugly. I mean mac checks. Can we, please, use sane kernel API like
> > > is_valid_ether_addr()?
> > 
> > Good idea! But will is_valid_ether_addr() check a larger range?
> > The comment of is_valid_ether_addr()(include/linux/etherdevice.h) says:
> >    Check that the Ethernet address (MAC) is not 00:00:00:00:00:00, is not
> >    a *multicast address*, and is not FF:FF:FF:FF:FF:FF.
> > 
> 
> I am not good an expert at networking stuff, but can multicast mac address
> be valid for purpose of Wi-Fi adapter? IIUC it's can't, but as I said
> before, I am not an expert

Me neither. :P I found some reference here:
https://en.wikipedia.org/wiki/Multicast_address#Ethernet

And in the implementation of
is_multicast_ether_addr()(include/linux/etherdevice.h), it checks one
bit of mac address to determine a multicast or not.

Probably some other kernel API could help.

thanks,
- w