Re: [Linux-kernel-mentees] [PATCH] net: usb: Fix uninit-was-stored issue in asix_read_cmd() - Greg Kroah-Hartman

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: netdev <netdev@vger.kernel.org>,
	USB list <linux-usb@vger.kernel.org>,
	syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Jakub Kicinski <kuba@kernel.org>,
	linux-kernel-mentees@lists.linuxfoundation.org,
	David Miller <davem@davemloft.net>,
	Dmitry Vyukov <dvyukov@google.com>,
	Himadri Pandya <himadrispandya@gmail.com>
Subject: Re: [Linux-kernel-mentees] [PATCH] net: usb: Fix uninit-was-stored issue in asix_read_cmd()
Date: Tue, 25 Aug 2020 17:44:15 +0200	[thread overview]
Message-ID: <20200825154415.GA1513396@kroah.com> (raw)
In-Reply-To: <20200825144437.GA1484901@kroah.com>

On Tue, Aug 25, 2020 at 04:44:37PM +0200, Greg Kroah-Hartman wrote:
> On Tue, Aug 25, 2020 at 10:39:46AM -0400, Alan Stern wrote:
> > On Tue, Aug 25, 2020 at 08:51:35AM +0200, Greg Kroah-Hartman wrote:
> > > At first glance, I think this can all be cleaned up, but it will take a
> > > bit of tree-wide work.  I agree, we need a "read this message and error
> > > if the whole thing is not there", as well as a "send this message and
> > > error if the whole thing was not sent", and also a way to handle
> > > stack-provided data, which seems to be the primary reason subsystems
> > > wrap this call (they want to make it easier on their drivers to use it.)
> > > 
> > > Let me think about this in more detail, but maybe something like:
> > > 	usb_control_msg_read()
> > > 	usb_control_msg_send()
> > > is a good first step (as the caller knows this) and stack provided data
> > > would be allowed, and it would return an error if the whole message was
> > > not read/sent properly.  That way we can start converting everything
> > > over to a sane, and checkable, api and remove a bunch of wrapper
> > > functions as well.
> > 
> > Suggestion: _read and _send are not a natural pair.  Consider instead
> > _read and _write.  _recv and _send don't feel right either, because it
> > both cases the host sends the control message -- the difference lies
> > in who sends the data.
> 
> Yes, naming is hard :)
> 
> 	usb_control_read_msg()
> 	usb_control_write_msg()
> 
> feels good to me, let me try this out and see if it actually makes sense
> to do this on a few in-usb-core files and various drivers...

Turns out we have a long history of using snd/rcv for USB control
messages:
	usb_rcvctrlpipe()
	usb_sndctrlpipe()

so while _recv and _send might feel a bit "odd", it is what we are used
to using, and when converting existing users, I can drop the pipe macro
from the calls, turning something like:
	usb_control_msg(hdev, usb_sndctrlpipe(hdev, 0), ...);
into:
	usb_control_send_msg(hdev, 0, ...);

or maybe:
	usb_control_msg_send(hdev, 0, ...);
with a full noun_verb pairing, instead of noun_verb_noun.

thanks,

greg k-h
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