linux-kernel - [PATCH 4.4 19/28] ALSA: line6: Fix leftover URB at error-path during probe

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Message-Id: <20171016160924.499818746@linuxfoundation.org>
Date:   Mon, 16 Oct 2017 18:12:12 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Andrey Konovalov <andreyknvl@...gle.com>,
        Takashi Iwai <tiwai@...e.de>
Subject: [PATCH 4.4 19/28] ALSA: line6: Fix leftover URB at error-path during probe

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Takashi Iwai <tiwai@...e.de>

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@...gle.com>
Tested-by: Andrey Konovalov <andreyknvl@...gle.com>
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 sound/usb/line6/driver.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

--- a/sound/usb/line6/driver.c
+++ b/sound/usb/line6/driver.c
@@ -586,9 +586,10 @@ int line6_probe(struct usb_interface *in
 	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);