[v2.6.34-stable 44/77] ALSA: hda/realtek - Fix Oops in alc_mux_select()

[Paul Gortmaker]

From: Takashi Iwai <tiwai@xxxxxxx>

                   -------------------
    This is a commit scheduled for the next v2.6.34 longterm release.
    http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git
    If you see a problem with using this for longterm, please comment.
                   -------------------

commit cce4aa378a049f4275416ee6302dd24f37b289df upstream.

When no imux is available (e.g. a single capture source),
alc_auto_init_input_src() may trigger an Oops due to the access to -1.
Add a proper zero-check to avoid it.

Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
[PG: in mainline, 21268961d3 rewrites and creates alc_mux_select, but the
code that needed the check still existed prior to that in alc_mux_enum_put]
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
---
 sound/pci/hda/patch_realtek.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/sound/pci/hda/patch_realtek.c b/sound/pci/hda/patch_realtek.c
index 94f1a80..28118fd 100644
--- a/sound/pci/hda/patch_realtek.c
+++ b/sound/pci/hda/patch_realtek.c
@@ -444,6 +444,8 @@ static int alc_mux_enum_put(struct snd_kcontrol *kcontrol,
 	imux = &spec->input_mux[mux_idx];
 	if (!imux->num_items && mux_idx > 0)
 		imux = &spec->input_mux[0];
+	if (!imux->num_items)
+		return 0;
 
 	type = get_wcaps_type(get_wcaps(codec, nid));
 	if (type == AC_WID_AUD_MIX) {
-- 
1.7.12.1

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