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

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Date:   Mon, 4 Apr 2022 18:31:51 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     David Kahurani <k.kahurani@...il.com>
Cc:     netdev@...r.kernel.org,
        syzbot+d3dbdf31fbe9d8f5f311@...kaller.appspotmail.com,
        davem@...emloft.net, jgg@...pe.ca, kuba@...nel.org,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        phil@...lpotter.co.uk, syzkaller-bugs@...glegroups.com,
        arnd@...db.de, paskripkin@...il.com
Subject: Re: [PATCH] net: ax88179: add proper error handling of usb read
 errors

> diff --git a/drivers/net/usb/ax88179_178a.c b/drivers/net/usb/ax88179_178a.c
> index e2fa56b92..b5e114bed 100644
> --- a/drivers/net/usb/ax88179_178a.c
> +++ b/drivers/net/usb/ax88179_178a.c
> @@ -185,8 +185,9 @@ static const struct {
>  	{7, 0xcc, 0x4c, 0x18, 8},
>  };
>  
> -static int __ax88179_read_cmd(struct usbnet *dev, u8 cmd, u16 value, u16 index,
> -			      u16 size, void *data, int in_pm)
> +static int __must_check __ax88179_read_cmd(struct usbnet *dev, u8 cmd,
> +		                           u16 value, u16 index, u16 size,
> +					   void *data, int in_pm)
>  {
>  	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.


> @@ -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