ALSA: line6: Fix leftover URB at error-path during probe

BugLink: http://bugs.launchpad.net/bugs/1724669
commit c95072b3d88fac4be295815f2b67df366c0c297f upstream.

While line6_probe() may kick off URB for a control MIDI endpoint, the
function doesn't clean up it properly at its error path.  This results
in a leftover URB action that is eventually triggered later and causes
an Oops like:
  general protection fault: 0000 [#1] PREEMPT SMP KASAN
  CPU: 1 PID: 0 Comm: swapper/1 Not tainted
  RIP: 0010:usb_fill_bulk_urb ./include/linux/usb.h:1619
  RIP: 0010:line6_start_listen+0x3fe/0x9e0 sound/usb/line6/driver.c:76
  Call Trace:
   <IRQ>
   line6_data_received+0x1f7/0x470 sound/usb/line6/driver.c:326
   __usb_hcd_giveback_urb+0x2e0/0x650 drivers/usb/core/hcd.c:1779
   usb_hcd_giveback_urb+0x337/0x420 drivers/usb/core/hcd.c:1845
   dummy_timer+0xba9/0x39f0 drivers/usb/gadget/udc/dummy_hcd.c:1965
   call_timer_fn+0x2a2/0x940 kernel/time/timer.c:1281
   ....

Since the whole clean-up procedure is done in line6_disconnect()
callback, we can simply call it in the error path instead of
open-coding the whole again.  It'll fix such an issue automagically.

The bug was spotted by syzkaller.

Fixes: eedd0e95d355 ("ALSA: line6: Don't forget to call driver's destructor at error path")
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Tested-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>

diff --git a/sound/usb/line6/driver.c b/sound/usb/line6/driver.c
index 0ff5a7d2e19fe1cc584a6420461841be26781b9b..c8f723c3a0336905d02afc8d33a51031985430e6 100644 (file)
--- a/sound/usb/line6/driver.c
+++ b/sound/usb/line6/driver.c
@@ -779,9 +779,10 @@ int line6_probe(struct usb_interface *interface,
        return 0;
 
  error:
-       if (line6->disconnect)
-               line6->disconnect(line6);
-       snd_card_free(card);
+       /* we can call disconnect callback here because no close-sync is
+        * needed yet at this point
+        */
+       line6_disconnect(interface);
        return ret;
 }
 EXPORT_SYMBOL_GPL(line6_probe);