[ 3.8.y.z extended stable ] Patch "ALSA: HDA: Fix Oops caused by dereference NULL pointer" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    ALSA: HDA: Fix Oops caused by dereference NULL pointer

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 2121a93efd106903f6b4d9bac6d2ce94ae4d2225 Mon Sep 17 00:00:00 2001
From: Wang YanQing <udknight at gmail.com>
Date: Tue, 7 May 2013 11:27:33 +0800
Subject: ALSA: HDA: Fix Oops caused by dereference NULL pointer

commit 2195b063f6609e4c6268f291683902f25eaf9aa6 upstream.

The interrupt handler azx_interrupt will call azx_update_rirb,
which may call snd_hda_queue_unsol_event, snd_hda_queue_unsol_event
will dereference chip->bus pointer.

The problem is we alloc chip->bus in azx_codec_create
which will be called after we enable IRQ and enable unsolicited
event in azx_probe.

This will cause Oops due dereference NULL pointer. I meet it, good luck:)

[Rearranged the NULL check before the tracepoint and added another
 NULL check of bus->workq -- tiwai]

Signed-off-by: Wang YanQing <udknight at gmail.com>
Signed-off-by: Takashi Iwai <tiwai at suse.de>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 sound/pci/hda/hda_codec.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sound/pci/hda/hda_codec.c b/sound/pci/hda/hda_codec.c
index 622f726..f283157 100644
--- a/sound/pci/hda/hda_codec.c
+++ b/sound/pci/hda/hda_codec.c
@@ -617,6 +617,9 @@ int snd_hda_queue_unsol_event(struct hda_bus *bus, u32 res, u32 res_ex)
 	struct hda_bus_unsolicited *unsol;
 	unsigned int wp;

+	if (!bus || !bus->workq)
+		return 0;
+
 	trace_hda_unsol_event(bus, res, res_ex);
 	unsol = bus->unsol;
 	if (!unsol)
--
1.8.1.2