linux-kernel - Re: [PATCH] net: ax88179: add proper error handling of usb read errors

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Date:   Wed, 13 Apr 2022 15:36:57 +0300
From:   David Kahurani <k.kahurani@...il.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     netdev@...r.kernel.org,
        syzbot <syzbot+d3dbdf31fbe9d8f5f311@...kaller.appspotmail.com>,
        davem@...emloft.net, jgg@...pe.ca, kuba@...nel.org,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        Phillip Potter <phil@...lpotter.co.uk>,
        syzkaller-bugs@...glegroups.com, arnd@...db.de,
        Pavel Skripkin <paskripkin@...il.com>
Subject: Re: [PATCH] net: ax88179: add proper error handling of usb read errors

On Mon, Apr 4, 2022 at 6:32 PM Dan Carpenter <dan.carpenter@...cle.com> wrote:

Hi Dan

> >       int ret;
> >       int (*fn)(struct usbnet *, u8, u8, u16, u16, void *, u16);
> > @@ -201,9 +202,12 @@ static int __ax88179_read_cmd(struct usbnet *dev, u8 cmd, u16 value, u16 index,
> >       ret = fn(dev, cmd, USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
> >                value, index, data, size);
> >
> > -     if (unlikely(ret < 0))
> > +     if (unlikely(ret < size)) {
> > +             ret = ret < 0 ? ret : -ENODATA;
> > +
> >               netdev_warn(dev->net, "Failed to read reg index 0x%04x: %d\n",
> >                           index, ret);
> > +     }
> >
> >       return ret;
>
> It would be better to make __ax88179_read_cmd() return 0 on success
> instead of returning size on success.  Non-standard returns lead to bugs.
>

I don't suppose this would have much effect on the structure of the
code and indeed plan to do this but just some minor clarification.

Isn't it standard for reader functions to return the number of bytes read?

Regards,
David.

>
> > @@ -1060,16 +1151,30 @@ static int ax88179_check_eeprom(struct usbnet *dev)
> >
> >               jtimeout = jiffies + delay;
> >               do {
> > -                     ax88179_read_cmd(dev, AX_ACCESS_MAC, AX_SROM_CMD,
> > -                                      1, 1, &buf);
> > +                 ret = ax88179_read_cmd(dev, AX_ACCESS_MAC, AX_SROM_CMD,
> > +                                        1, 1, &buf);
> > +
> > +                 if (ret < 0) {
> > +                         netdev_dbg(dev->net,
> > +                                    "Failed to read SROM_CMD: %d\n",
> > +                                    ret);
> > +                         return ret;
> > +                 }
> >
> >                       if (time_after(jiffies, jtimeout))
> >                               return -EINVAL;
>
> The indenting here is wrong.  Run scripts/checkpatch.pl on your patches.
>
> regards,
> dan carpenter
>