Re: [PATCH v3] USB: serial: quatech2: Fix null-ptr-deref in qt2_process_read_urb()

[Qasim Ijaz <qasdev00@gmail.com>]

On Tue, Jan 14, 2025 at 10:47:33AM +0100, Johan Hovold wrote:
> On Mon, Jan 13, 2025 at 06:00:34PM +0000, Qasim Ijaz wrote:
> > This patch addresses a null-ptr-deref in qt2_process_read_urb() due to
> > an incorrect bounds check in the following:
> > 
> >        if (newport > serial->num_ports) {
> >                dev_err(&port->dev,
> >                        "%s - port change to invalid port: %i\n",
> >                        __func__, newport);
> >                break;
> >        }
> > 
> > The condition doesn't account for the valid range of the serial->port
> > buffer, which is from 0 to serial->num_ports - 1. When newport is equal
> > to serial->num_ports, the assignment of "port" in the
> > following code is out-of-bounds and NULL:
> > 
> >        serial_priv->current_port = newport;
> >        port = serial->port[serial_priv->current_port];
> > 
> > The fix checks if newport is greater than or equal to serial->num_ports
> > indicating it is out-of-bounds.
> > 
> > Reported-by: syzbot <syzbot+506479ebf12fe435d01a@syzkaller.appspotmail.com>
> > Closes: https://syzkaller.appspot.com/bug?extid=506479ebf12fe435d01a
> > Fixes: f7a33e608d9a ("USB: serial: add quatech2 usb to serial driver")
> > Cc: <stable@vger.kernel.org>      # 3.5
> > Signed-off-by: Qasim Ijaz <qasdev00@gmail.com>
> > ---
> 
> Thanks for the update. I've applied the patch now after adding Greg's
> Reviewed-by tag (for v2).
> 
> For your future contributions, try to remember to include any
> Reviewed-by or Tested-by tags when updating the patch unless the changes
> are non-trivial.
> 
> There should typically also be a short change log here under the ---
> line to indicate what changes from previous versions.
> 
> It is also encouraged to write the commit message in imperative mood
> (add, change, fix) and to avoid the phrase "this patch". There are some
> more details in
> 
> 	Documentation/process/submitting-patches.rst
> 
> Something to keep in mind for the future, but this patch already looks
> really good.
> 
> Johan

Hi Johan,

Thanks for reviewing and applying the patch. I appreciate the guidance on patch style and process, and I'll incorporate your suggestions in future submissions.

Best regards,
Qasim