linux-kernel - Re: gadgetfs broken since 7f7f25e8

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Date:	Tue, 3 Mar 2015 21:42:49 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Alexander Holler <holler@...oftware.de>,
	Richard Weinberger <richard.weinberger@...il.com>,
	USB list <linux-usb@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>, Felipe Balbi <balbi@...com>
Subject: Re: gadgetfs broken since 7f7f25e8

On Tue, Mar 03, 2015 at 10:47:14AM -0500, Alan Stern wrote:
> On Tue, 3 Mar 2015, Al Viro wrote:
> 
> > Looking at that thing again...  why do they need to be dummy?  After all,
> > those methods start with get_ready_ep(), which will fail unless we have
> > ->state == STATE_EP_ENABLED.  So they'd be failing just fine until that
> > first write() anyway.  Let's do the following:
> 
> In addition to the changes you made, it looks like you will need the 
> following or something similar (also untested).  I'm not sure if this 
> is race-free, but it's better than before.

Right, ep0 has the same kind of problem...


> @@ -1240,6 +1241,10 @@ static int
>  ep0_fasync (int f, struct file *fd, int on)
>  {
>  	struct dev_data		*dev = fd->private_data;
> +
> +	if (dev->state <= STATE_DEV_OPENED)
> +		return -ENODEV;
> +

Er...  What is protecting dev->state here?  Matter of fact, what's the
point of that check at all?  Right now you have .fasync = ep0_fasync
both in ep0_io_operations and in dev_init_operations, so your delta
changes the existing semantics...
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