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

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Message-ID: <20170207130102.GA24330@kroah.com>
Date:   Tue, 7 Feb 2017 14:01:02 +0100
From:   Greg KH <greg@...ah.com>
To:     Petko Manolov <petkan@...leusys.com>
Cc:     Ben Hutchings <ben@...adent.org.uk>,
        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 Tue, Feb 07, 2017 at 02:53:24PM +0200, Petko Manolov wrote:
> On 17-02-07 11:51:31, Greg KH wrote:
> > On Tue, Feb 07, 2017 at 12:34:52PM +0200, Petko Manolov wrote:
> > > 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.
> > 
> > make up my mind about what?  These are bugs, they should be fixed, I'm not 
> > taking a total api change at this point in time, sorry.
> 
> Exactly what i said above: " ... shoud not happen in the stable releases".  
> 
> Would you consider what David proposed (usb_control_msg_with_malloc()) for 4.11, 
> for example?  I for one will use something like that in all my drivers.

Sure, but you might want to make it a bit smaller of a function name :)