Patch "ALSA: seq: Cancel pending autoload work at unbinding device" has been added to the 4.13-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    ALSA: seq: Cancel pending autoload work at unbinding device

to the 4.13-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     alsa-seq-cancel-pending-autoload-work-at-unbinding-device.patch
and it can be found in the queue-4.13 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From fc27fe7e8deef2f37cba3f2be2d52b6ca5eb9d57 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Tue, 12 Sep 2017 12:41:20 +0200
Subject: ALSA: seq: Cancel pending autoload work at unbinding device

From: Takashi Iwai <tiwai@suse.de>

commit fc27fe7e8deef2f37cba3f2be2d52b6ca5eb9d57 upstream.

ALSA sequencer core has a mechanism to load the enumerated devices
automatically, and it's performed in an off-load work.  This seems
causing some race when a sequencer is removed while the pending
autoload work is running.  As syzkaller spotted, it may lead to some
use-after-free:
  BUG: KASAN: use-after-free in snd_rawmidi_dev_seq_free+0x69/0x70
  sound/core/rawmidi.c:1617
  Write of size 8 at addr ffff88006c611d90 by task kworker/2:1/567

  CPU: 2 PID: 567 Comm: kworker/2:1 Not tainted 4.13.0+ #29
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
  Workqueue: events autoload_drivers
  Call Trace:
   __dump_stack lib/dump_stack.c:16 [inline]
   dump_stack+0x192/0x22c lib/dump_stack.c:52
   print_address_description+0x78/0x280 mm/kasan/report.c:252
   kasan_report_error mm/kasan/report.c:351 [inline]
   kasan_report+0x230/0x340 mm/kasan/report.c:409
   __asan_report_store8_noabort+0x1c/0x20 mm/kasan/report.c:435
   snd_rawmidi_dev_seq_free+0x69/0x70 sound/core/rawmidi.c:1617
   snd_seq_dev_release+0x4f/0x70 sound/core/seq_device.c:192
   device_release+0x13f/0x210 drivers/base/core.c:814
   kobject_cleanup lib/kobject.c:648 [inline]
   kobject_release lib/kobject.c:677 [inline]
   kref_put include/linux/kref.h:70 [inline]
   kobject_put+0x145/0x240 lib/kobject.c:694
   put_device+0x25/0x30 drivers/base/core.c:1799
   klist_devices_put+0x36/0x40 drivers/base/bus.c:827
   klist_next+0x264/0x4a0 lib/klist.c:403
   next_device drivers/base/bus.c:270 [inline]
   bus_for_each_dev+0x17e/0x210 drivers/base/bus.c:312
   autoload_drivers+0x3b/0x50 sound/core/seq_device.c:117
   process_one_work+0x9fb/0x1570 kernel/workqueue.c:2097
   worker_thread+0x1e4/0x1350 kernel/workqueue.c:2231
   kthread+0x324/0x3f0 kernel/kthread.c:231
   ret_from_fork+0x25/0x30 arch/x86/entry/entry_64.S:425

The fix is simply to assure canceling the autoload work at removing
the device.

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>

---
 sound/core/seq_device.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/sound/core/seq_device.c
+++ b/sound/core/seq_device.c
@@ -148,8 +148,10 @@ void snd_seq_device_load_drivers(void)
 	flush_work(&autoload_work);
 }
 EXPORT_SYMBOL(snd_seq_device_load_drivers);
+#define cancel_autoload_drivers()	cancel_work_sync(&autoload_work)
 #else
 #define queue_autoload_drivers() /* NOP */
+#define cancel_autoload_drivers() /* NOP */
 #endif
 
 /*
@@ -159,6 +161,7 @@ static int snd_seq_device_dev_free(struc
 {
 	struct snd_seq_device *dev = device->device_data;
 
+	cancel_autoload_drivers();
 	put_device(&dev->dev);
 	return 0;
 }


Patches currently in stable-queue which might be from tiwai@suse.de are

queue-4.13/alsa-seq-cancel-pending-autoload-work-at-unbinding-device.patch