From mboxrd@z Thu Jan 1 00:00:00 1970 From: Johan Hovold Subject: Re: [PATCH v2 4/9] ALSA: line6: Add a sanity check for invalid EPs Date: Wed, 11 Oct 2017 16:52:09 +0200 Message-ID: <20171011145209.GE4269@localhost> References: <20171011103646.11879-1-tiwai@suse.de> <20171011103646.11879-5-tiwai@suse.de> <20171011142837.GZ4269@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-usb-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Takashi Iwai Cc: Johan Hovold , alsa-devel-K7yf7f+aM1XWsZ/bQMPhNw@public.gmane.org, linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Andrey Konovalov , Greg KH List-Id: alsa-devel@alsa-project.org On Wed, Oct 11, 2017 at 04:45:16PM +0200, Takashi Iwai wrote: > On Wed, 11 Oct 2017 16:28:37 +0200, > Johan Hovold wrote: > > > > On Wed, Oct 11, 2017 at 12:36:41PM +0200, Takashi Iwai wrote: > > > As syzkaller spotted, currently line6 drivers submit a URB with the > > > fixed EP without checking whether it's actually available, which may > > > result in a kernel warning like: > > > usb 1-1: BOGUS urb xfer, pipe 3 != type 1 > > > ------------[ cut here ]------------ > > > WARNING: CPU: 0 PID: 24 at drivers/usb/core/urb.c:449 > > > usb_submit_urb+0xf8a/0x11d0 > > > Modules linked in: > > > CPU: 0 PID: 24 Comm: kworker/0:1 Not tainted 4.14.0-rc2-42613-g1488251d1a98 #238 > > > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 > > > Workqueue: usb_hub_wq hub_event > > > Call Trace: > > > line6_start_listen+0x55f/0x9e0 sound/usb/line6/driver.c:82 > > > line6_init_cap_control sound/usb/line6/driver.c:690 > > > line6_probe+0x7c9/0x1310 sound/usb/line6/driver.c:764 > > > podhd_probe+0x64/0x70 sound/usb/line6/podhd.c:474 > > > usb_probe_interface+0x35d/0x8e0 drivers/usb/core/driver.c:361 > > > .... > > > > > > This patch adds a sanity check of validity of EPs at the device > > > initialization phase for avoiding the call with an invalid EP. > > > > > > Reported-by: Andrey Konovalov > > > Tested-by: Andrey Konovalov > > > Signed-off-by: Takashi Iwai > > > --- > > > sound/usb/line6/driver.c | 7 +++++++ > > > 1 file changed, 7 insertions(+) > > > > > > diff --git a/sound/usb/line6/driver.c b/sound/usb/line6/driver.c > > > index 0ff5a7d2e19f..0da6f68761e3 100644 > > > --- a/sound/usb/line6/driver.c > > > +++ b/sound/usb/line6/driver.c > > > @@ -78,6 +78,13 @@ static int line6_start_listen(struct usb_line6 *line6) > > > line6->buffer_listen, LINE6_BUFSIZE_LISTEN, > > > line6_data_received, line6); > > > } > > > + > > > + /* sanity checks of EP before actually submitting */ > > > + if (usb_urb_ep_type_check(line6->urb_listen)) { > > > + dev_err(line6->ifcdev, "invalid control EP\n"); > > > + return -EINVAL; > > > + } > > > > You're now doing this check twice (here and in usb_submit_urb) every > > time this URB is submitted rather just checking it once in probe. > > > > Seems like a quick band-aid to me. > > Yes, it is :) > > We may split line6_start_listen() to two functions, one for > initializing URBs and another for submission, but it'll be more codes > and the check is fairly cheap. So again it's a question whether > easier to read or to get minor optimization. I'd say it's also a question about long-term maintainability. Those quick band-aids tend to keep piling up over time. Johan -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html