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

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Message-ID: <65c52645-26e8-ff2b-86dc-b5dd697317f9@gmail.com>
Date:   Sat, 16 Apr 2022 14:10:02 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     David Kahurani <k.kahurani@...il.com>, netdev@...r.kernel.org
Cc:     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, dan.carpenter@...cle.com
Subject: Re: [PATCH] net: ax88179: add proper error handling of usb read
 errors

Hi David,

one more small comment

On 4/16/22 10:48, David Kahurani wrote:
> Reads that are lesser than the requested size lead to uninit-value bugs.
> In this particular case a variable which was supposed to be initialized
> after a read is left uninitialized after a partial read.
> 
> Qualify such reads as errors and handle them correctly and while at it
> convert the reader functions to return zero on success for easier error
> handling.
> 
> Fixes: e2ca90c276e1 ("ax88179_178a: ASIX AX88179_178A USB 3.0/2.0 to
> gigabit ethernet adapter driver")
> Signed-off-by: David Kahurani <k.kahurani@...il.com>
> Reported-and-tested-by: syzbot+d3dbdf31fbe9d8f5f311@...kaller.appspotmail.com
> ---

[code snip]

> @@ -1295,6 +1439,7 @@ static int ax88179_led_setting(struct usbnet *dev)
>   static void ax88179_get_mac_addr(struct usbnet *dev)
>   {
>   	u8 mac[ETH_ALEN];
> +	int ret;
>   
>   	memset(mac, 0, sizeof(mac));
>   
> @@ -1303,8 +1448,12 @@ static void ax88179_get_mac_addr(struct usbnet *dev)
>   		netif_dbg(dev, ifup, dev->net,
>   			  "MAC address read from device tree");
>   	} else {
> -		ax88179_read_cmd(dev, AX_ACCESS_MAC, AX_NODE_ID, ETH_ALEN,
> -				 ETH_ALEN, mac);
> +		ret = ax88179_read_cmd(dev, AX_ACCESS_MAC, AX_NODE_ID, ETH_ALEN,
> +				       ETH_ALEN, mac);
> +
> +		if (ret)
> +			netdev_dbg(dev->net, "Failed to read NODE_ID: %d", ret);
> +
>   		netif_dbg(dev, ifup, dev->net,
>   			  "MAC address read from ASIX chip");
>   	}


This message sequence is confusing.

In case of ax88179_read_cmd() failure mac read from device actually 
failed, but message says, that it was successfully finished.





With regards,
Pavel Skripkin

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