linux-kernel - Re: [PATCH] net: usb: Fix uninit-was-stored issue in asix_read_phy

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Date:   Thu, 27 Aug 2020 10:52:15 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     Himadri Pandya <himadrispandya@...il.com>
Cc:     davem@...emloft.net, kuba@...nel.org, linux-usb@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzkaller-bugs@...glegroups.com,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        gregkh@...uxfoundation.org
Subject: Re: [PATCH] net: usb: Fix uninit-was-stored issue in
 asix_read_phy_addr()

On Thu, Aug 27, 2020 at 12:23:55PM +0530, Himadri Pandya wrote:
> The buffer size is 2 Bytes and we expect to receive the same amount of
> data. But sometimes we receive less data and run into uninit-was-stored
> issue upon read. Hence modify the error check on the return value to match
> with the buffer size as a prevention.
> 
> Reported-and-tested by: syzbot+a7e220df5a81d1ab400e@...kaller.appspotmail.com
> Signed-off-by: Himadri Pandya <himadrispandya@...il.com>
> ---
>  drivers/net/usb/asix_common.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/usb/asix_common.c b/drivers/net/usb/asix_common.c
> index e39f41efda3e..7bc6e8f856fe 100644
> --- a/drivers/net/usb/asix_common.c
> +++ b/drivers/net/usb/asix_common.c
> @@ -296,7 +296,7 @@ int asix_read_phy_addr(struct usbnet *dev, int internal)
>  
>  	netdev_dbg(dev->net, "asix_get_phy_addr()\n");
>  
> -	if (ret < 0) {
> +	if (ret < 2) {
>  		netdev_err(dev->net, "Error reading PHYID register: %02x\n", ret);
>  		goto out;
>  	}

If ret is 0 or 1 here, shouldn't asix_read_phy_addr() return an error code
instead of 0 or 1?

- Eric