linux-kernel - Re: [PATCH] usb: interface: allow drivers declare number of endpoints they need

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Message-ID: <20151130222034.GA20749@dtor-ws>
Date:	Mon, 30 Nov 2015 14:20:34 -0800
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Felipe Balbi <balbi@...com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Vladis Dronov <vdronov@...hat.com>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: interface: allow drivers declare number of
 endpoints they need

On Mon, Nov 30, 2015 at 03:39:43PM -0600, Felipe Balbi wrote:
> 
> Hi,
> 
> Dmitry Torokhov <dmitry.torokhov@...il.com> writes:
> > USB interface drivers need to check number of endpoints before trying to
> > access/use them. Quite a few drivers only use the default setting
> > (altsetting 0), so let's allow them to declare number of endpoints in
> > altsetting 0 they require to operate and have USB core check it for us
> > instead of having every driver implement check manually.
> >
> > For compatibility, if driver does not specify number of endpoints (i.e.
> > number of endpoints is left at 0) we bypass the check in USB core and
> > expect the driver perform necessary checks on its own.
> >
> > Acked-by: Alan Stern <stern@...land.harvard.edu>
> > Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
> > ---
> >
> > Greg, if the patch is reasonable I wonder if I can take it through my
> > tree, as I have a few drivers that do not check number of endpoints
> > properly and will crash the kernel when specially crafted device is
> > plugged in, as reported by Vladis Dronov.
> >
> >  drivers/usb/core/driver.c | 9 +++++++++
> >  include/linux/usb.h       | 7 +++++++
> >  2 files changed, 16 insertions(+)
> >
> > diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
> > index 6b5063e..d9f680d 100644
> > --- a/drivers/usb/core/driver.c
> > +++ b/drivers/usb/core/driver.c
> > @@ -306,6 +306,15 @@ static int usb_probe_interface(struct device *dev)
> >  
> >  	dev_dbg(dev, "%s - got id\n", __func__);
> >  
> > +	if (driver->num_endpoints &&
> 
> this part of the check is pointless, right ?
> 
> > +	    intf->altsetting[0].desc.bNumEndpoints < driver->num_endpoints) {
> 
> bNumEndpoints will never be less than 0 and if it is, we're gonna have
> issues elsewhere anyway.

Fair enough, I'll drop it.

Thanks.

-- 
Dmitry
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