Re: ftdi_sio BUG: NULL pointer dereference

[Mike Remski]

On 06/04/2014 10:52 AM, Johan Hovold wrote:
> On Wed, Jun 04, 2014 at 10:29:37AM -0400, Mike Remski wrote:
> > On 06/04/2014 10:19 AM, Johan Hovold wrote:
> > > >From 4ddea3a573b8c15beefb67bc35c440850063d79d Mon Sep 17 00:00:00 2001
> > > From: Johan Hovold <johan@xxxxxxxxxx>
> > > Date: Wed, 4 Jun 2014 14:09:43 +0200
> > > Subject: [PATCH 1/5] USB: ftdi_sio: fix null deref at port probe
> > >
> > > Fix NULL-pointer dereference when probing an interface with no
> > > endpoints.
> > >
> > > These devices have two bulk endpoints per interface, but this avoids
> > > crashing the kernel if a user forces a non-FTDI device to be probed.
> > >
> > > Note that the iterator variable was made unsigned in order to avoid
> > > a maybe-uninitialized compiler warning for ep_desc after the loop.
> > >
> > > Fixes: 895f28badce9 ("USB: ftdi_sio: fix hi-speed device packet size
> > > calculation")
> > >
> > > Reported-by: Mike Remski <mremski@xxxxxxxxxxxxx>
> > > Cc: <stable@xxxxxxxxxxxxxxx>	# 2.3.61
> > > Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
> > > ---
> > >    drivers/usb/serial/ftdi_sio.c | 7 +++++--
> > >    1 file changed, 5 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
> > > index 7c6e1dedeb06..3019141397eb 100644
> > > --- a/drivers/usb/serial/ftdi_sio.c
> > > +++ b/drivers/usb/serial/ftdi_sio.c
> > > @@ -1564,14 +1564,17 @@ static void ftdi_set_max_packet_size(struct usb_serial_port *port)
> > >    	struct usb_device *udev = serial->dev;
> > >    
> > >    	struct usb_interface *interface = serial->interface;
> > > -	struct usb_endpoint_descriptor *ep_desc = &interface->cur_altsetting->endpoint[1].desc;
> > > +	struct usb_endpoint_descriptor *ep_desc;
> > >    
> > >    	unsigned num_endpoints;
> > > -	int i;
> > > +	unsigned i;
> > >    
> > >    	num_endpoints = interface->cur_altsetting->desc.bNumEndpoints;
> > >    	dev_info(&udev->dev, "Number of endpoints %d\n", num_endpoints);
> > >    
> > > +	if (!num_endpoints)
> > > +		return;
> > > +
> > >    	/* NOTE: some customers have programmed FT232R/FT245R devices
> > >    	 * with an endpoint size of 0 - not good.  In this case, we
> > >    	 * want to override the endpoint descriptor setting and use a
> > Thanks Johan.  I tried to get the cdc_acm working;  did not have much
> > luck/time (typical overcommit on workload) I will retry with the commit
> > mentioned.
> > I will try the patch today and get back to you.  Nice on the ep_desc:
> > looking at the code priv->max_packet_size is attached to the port, your
> > change would use the last thing off of cur_altsetting->endpoint[], but
> > I'm wondering if we should actually be setting priv->max_packet_size to
> > whatever the max is of all endpoint[].desc->wMaxPacketSize?
> >
> > Thoughts?
> This is the exact same behaviour as the old code (minus the NULL-deref).
>
> These device have two bulk endpoints per interface and they are supposed
> to be using the same max packet size (64 or 512 depending on device and
> host).
>
> This value is also used during depacketisation of incoming data (and
> packetisation of outgoing data for legacy devices). I'm pretty convinced
> you're using the wrong driver, something which would lead to corruption
> of incoming data when the (non-existing) status bytes are stripped from
> the stream.
>
> You really should try cdc-acm.
>
> Johan

Thanks for the explaination.  Yes, I am working on trying cdc-acm.

--
Office: (978)401-4032 (x123 internally)
Cell: (603) 759-6953

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/