[14/94] ALSA: HDA: Fix Oops caused by dereference NULL pointer

[Ben Hutchings]

3.2.46-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Wang YanQing <udknight@xxxxxxxxx>

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@xxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 sound/pci/hda/hda_codec.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/sound/pci/hda/hda_codec.c
+++ b/sound/pci/hda/hda_codec.c
@@ -615,6 +615,9 @@ int snd_hda_queue_unsol_event(struct hda
 	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)

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