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

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Message-ID: <20170207103452.zb4frzltpdjaaf2s@p310>
Date:   Tue, 7 Feb 2017 12:34:52 +0200
From:   Petko Manolov <petkan@...leusys.com>
To:     Ben Hutchings <ben@...adent.org.uk>
Cc:     David Laight <David.Laight@...LAB.COM>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
Subject: Re: [PATCH net 2/4] rtl8150: Use heap buffers for all register access

On 17-02-06 16:25:20, Ben Hutchings wrote:
> 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;

Since we return what usb_control_msg() told us to return i assume the error code 
will be available to anybody who cares.

> > 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.

Right, first thing first.

I am in favor of changing the API, but this should not happen in the stable 
releases.  I hope Greg will make up his mind and let us know.


cheers,
Petko