netdev - Re: [PATCH net 2/4] rtl8150: Use heap buffers for all register access

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Message-ID: <20170206162520.GA3442@decadent.org.uk>
Date:   Mon, 6 Feb 2017 16:25:20 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     David Laight <David.Laight@...LAB.COM>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        Petko Manolov <petkan@...leusys.com>
Subject: Re: [PATCH net 2/4] rtl8150: Use heap buffers for all register access

On Mon, Feb 06, 2017 at 04:09:18PM +0000, David Laight wrote:
> From: Ben Hutchings
[...]
> > +	ret = usb_control_msg(dev->udev, usb_rcvctrlpipe(dev->udev, 0),
> > +			      RTL8150_REQ_GET_REGS, RTL8150_REQT_READ,
> > +			      indx, 0, buf, size, 500);
> > +	if (ret > 0 && ret <= size)
> > +		memcpy(data, buf, ret);
> 
> If ret > size something is horridly wrong.
> Silently not updating the callers buffer at all cannot be right.

Yes, it seems strange to check this.  I originally wrote this as ret >
0, but then I checked the usbnet core and found __usbnet_read_cmd()
has the second comparison as well.

> > +	kfree(buf);
> > +	return ret;
> 
> I can't help feeling that it would be better to add a wrapper to
> usb_control_msg() that does the kmalloc() and memcpy()s and
> drop that into all the call sites.

It might be.  Right now I'm trying to patch up a bunch of regressions
rather than argue over an API change.

Ben.

-- 
Ben Hutchings
Experience is what causes a person to make new mistakes instead of old ones.

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