Patch "ALSA: usb-audio: Avoid calling usb_autopm_put_interface() at disconnect" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

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

    ALSA: usb-audio: Avoid calling usb_autopm_put_interface() at disconnect

to the 4.4-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-usb-audio-avoid-calling-usb_autopm_put_interface-at-disconnect.patch
and it can be found in the queue-4.4 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 5c06d68bc2a174a6b82dce9f100f55173b9a5189 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Tue, 12 Jan 2016 14:03:33 +0100
Subject: ALSA: usb-audio: Avoid calling usb_autopm_put_interface() at disconnect

From: Takashi Iwai <tiwai@suse.de>

commit 5c06d68bc2a174a6b82dce9f100f55173b9a5189 upstream.

ALSA PCM may still have a leftover instance after disconnection and
it delays its release.  The problem is that the PCM close code path of
USB-audio driver has a call of snd_usb_autosuspend().  This involves
with the call of usb_autopm_put_interface() and it may lead to a
kernel Oops due to the NULL object like:

 BUG: unable to handle kernel NULL pointer dereference at 0000000000000190
 IP: [<ffffffff815ae7ef>] usb_autopm_put_interface+0xf/0x30 PGD 0
 Call Trace:
  [<ffffffff8173bd94>] snd_usb_autosuspend+0x14/0x20
  [<ffffffff817461bc>] snd_usb_pcm_close.isra.14+0x5c/0x90
  [<ffffffff8174621f>] snd_usb_playback_close+0xf/0x20
  [<ffffffff816ef58a>] snd_pcm_release_substream.part.36+0x3a/0x90
  [<ffffffff816ef6b3>] snd_pcm_release+0xa3/0xb0
  [<ffffffff816debb0>] snd_disconnect_release+0xd0/0xe0
  [<ffffffff8114d417>] __fput+0x97/0x1d0
  [<ffffffff8114d589>] ____fput+0x9/0x10
  [<ffffffff8109e452>] task_work_run+0x72/0x90
  [<ffffffff81088510>] do_exit+0x280/0xa80
  [<ffffffff8108996a>] do_group_exit+0x3a/0xa0
  [<ffffffff8109261f>] get_signal+0x1df/0x540
  [<ffffffff81040903>] do_signal+0x23/0x620
  [<ffffffff8114c128>] ? do_readv_writev+0x128/0x200
  [<ffffffff810012e1>] prepare_exit_to_usermode+0x91/0xd0
  [<ffffffff810013ba>] syscall_return_slowpath+0x9a/0x120
  [<ffffffff817587cd>] ? __sys_recvmsg+0x5d/0x70
  [<ffffffff810d2765>] ? ktime_get_ts64+0x45/0xe0
  [<ffffffff8115dea0>] ? SyS_poll+0x60/0xf0
  [<ffffffff818d2327>] int_ret_from_sys_call+0x25/0x8f

We have already a check of disconnection in snd_usb_autoresume(), but
the check is missing its counterpart.  The fix is just to put the same
check in snd_usb_autosuspend(), too.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=109431
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 sound/usb/card.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -675,6 +675,8 @@ int snd_usb_autoresume(struct snd_usb_au
 
 void snd_usb_autosuspend(struct snd_usb_audio *chip)
 {
+	if (atomic_read(&chip->shutdown))
+		return;
 	if (atomic_dec_and_test(&chip->active))
 		usb_autopm_put_interface(chip->pm_intf);
 }


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

queue-4.4/alsa-hrtimer-fix-stall-by-hrtimer_cancel.patch
queue-4.4/alsa-hda-fix-white-noise-on-dell-latitude-e5550.patch
queue-4.4/alsa-hda-fix-the-headset-mic-detection-problem-for-a-dell-laptop.patch
queue-4.4/alsa-timer-harden-slave-timer-list-handling.patch
queue-4.4/alsa-timer-fix-double-unlink-of-active_list.patch
queue-4.4/alsa-control-avoid-kernel-warnings-from-tlv-ioctl-with-numid-0.patch
queue-4.4/alsa-hda-flush-the-pending-probe-work-at-remove.patch
queue-4.4/alsa-hda-fixup-inverted-internal-mic-for-lenovo-e50-80.patch
queue-4.4/alsa-usb-add-native-dsd-support-for-oppo-ha-1.patch
queue-4.4/alsa-hda-fix-missing-module-loading-with-model-generic-option.patch
queue-4.4/alsa-seq-fix-race-at-timer-setup-and-close.patch
queue-4.4/alsa-pcm-fix-snd_pcm_hw_params-struct-copy-in-compat-mode.patch
queue-4.4/alsa-seq-fix-snd_seq_call_port_info_ioctl-in-compat-mode.patch
queue-4.4/alsa-seq-fix-missing-null-check-at-remove_events-ioctl.patch
queue-4.4/alsa-usb-audio-fix-mixer-ctl-regression-of-native-instrument-devices.patch
queue-4.4/alsa-timer-handle-disconnection-more-safely.patch
queue-4.4/alsa-hda-fix-bass-pin-fixup-for-asus-n550jx.patch
queue-4.4/alsa-timer-fix-race-among-timer-ioctls.patch
queue-4.4/alsa-hda-add-fixup-for-dell-latitidue-e6540.patch
queue-4.4/alsa-usb-audio-avoid-calling-usb_autopm_put_interface-at-disconnect.patch