linux-kernel - Re: [PATCH 2/2][next] net: usb: asix: ax88772: net: Fix less than zero comparison of a u16

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Message-ID: <20210609115202.ms32g2rwco56iygz@pengutronix.de>
Date:   Wed, 9 Jun 2021 13:52:02 +0200
From:   Oleksij Rempel <o.rempel@...gutronix.de>
To:     Colin Ian King <colin.king@...onical.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Oleksij Rempel <linux@...pel-privat.de>,
        linux-usb@...r.kernel.org, netdev@...r.kernel.org,
        kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2][next] net: usb: asix: ax88772: net: Fix less than
 zero comparison of a u16

On Wed, Jun 09, 2021 at 10:51:09AM +0100, Colin Ian King wrote:
> On 08/06/2021 19:11, Oleksij Rempel wrote:
> > On Tue, Jun 08, 2021 at 04:22:49PM +0100, Colin King wrote:
> >> From: Colin Ian King <colin.king@...onical.com>
> >>
> >> The comparison of the u16 priv->phy_addr < 0 is always false because
> >> phy_addr is unsigned. Fix this by assigning the return from the call
> >> to function asix_read_phy_addr to int ret and using this for the
> >> less than zero error check comparison.
> >>
> >> Addresses-Coverity: ("Unsigned compared against 0")
> >> Fixes: 7e88b11a862a ("net: usb: asix: refactor asix_read_phy_addr() and handle errors on return")
> > 
> > Here is wrong Fixes tag. This assignment was bogus before this patch.
> 
> I'm not sure that's correct, that commit has the following change in it:
> 
> diff --git a/drivers/net/usb/ax88172a.c b/drivers/net/usb/ax88172a.c
> index b404c9462dce..c8ca5187eece 100644
> --- a/drivers/net/usb/ax88172a.c
> +++ b/drivers/net/usb/ax88172a.c
> @@ -220,6 +220,11 @@ static int ax88172a_bind(struct usbnet *dev, struct
> usb_interface *intf)
>         }
> 
>         priv->phy_addr = asix_read_phy_addr(dev, priv->use_embdphy);
> +       if (priv->phy_addr < 0) {
> +               ret = priv->phy_addr;
> +               goto free;
> +       }
> +
> 

Even before my patch asix_read_phy_addr() was returning different
error values. My patch just add check for the return value.

> > 
> >> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> >> ---
> >>  drivers/net/usb/ax88172a.c | 3 ++-
> >>  1 file changed, 2 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/net/usb/ax88172a.c b/drivers/net/usb/ax88172a.c
> >> index 2e2081346740..e24773bb9398 100644
> >> --- a/drivers/net/usb/ax88172a.c
> >> +++ b/drivers/net/usb/ax88172a.c
> >> @@ -205,7 +205,8 @@ static int ax88172a_bind(struct usbnet *dev, struct usb_interface *intf)
> >>  		goto free;
> >>  	}
> >>  
> >> -	priv->phy_addr = asix_read_phy_addr(dev, priv->use_embdphy);
> >> +	ret = asix_read_phy_addr(dev, priv->use_embdphy);
> >> +	priv->phy_addr = ret;
> > 
> > Ah.. it is same bug in different color :)
> > You probably wonted to do:
> > 	if (ret < 0)
> > 		goto free;
> > 
> > 	priv->phy_addr = ret;
> 
> Doh, brain failure of mine. I'll send a V2 later today.
> 
> > 
> >>  	if (priv->phy_addr < 0) {
> >>  		ret = priv->phy_addr;
> >>  		goto free;
> >> -- 
> >> 2.31.1
> >>
> >>
> > 
> 
> 

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