linux-kernel - [PATCH 4.14 093/193] ALSA: hda: Fix too short HDMI/DP chmap reporting

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Message-Id: <20171128100617.613571382@linuxfoundation.org>
Date:   Tue, 28 Nov 2017 11:25:40 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, VDR User <user.vdr@...il.com>,
        Takashi Iwai <tiwai@...e.de>
Subject: [PATCH 4.14 093/193] ALSA: hda: Fix too short HDMI/DP chmap reporting

4.14-stable review patch.  If anyone has any objections, please let me know.

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

From: Takashi Iwai <tiwai@...e.de>

commit c2432466f583cb719b35a41e757da587d9ab1d00 upstream.

We got a regression report about the HD-audio HDMI chmap, where some
surround channels are reported as UNKNOWN.  The git bisection pointed
the culprit at the commit 9b3dc8aa3fb1 ("ALSA: hda - Register chmap
obj as priv data instead of codec").  The story behind scene is like
this:

- While moving the code out of the legacy HDA to the HDA common place,
  the patch modifies the code to obtain the chmap array indirectly in
  a byte array, and it expands it to kctl value array.
- At the latter operation, the size of the array is wrongly passed by
  sizeof() to the pointer.
- It can be 4 on 32bit arch, thus too short for 6+ channels.
  (And that's the reason why it didn't hit other persons; it's 8 on
  64bit arch, thus it's usually enough.)

The code was further changed meanwhile, but the problem persisted.
Let's fix it by correctly evaluating the array size.

Fixes: 9b3dc8aa3fb1 ("ALSA: hda - Register chmap obj as priv data instead of codec")
Reported-by: VDR User <user.vdr@...il.com>
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 sound/hda/hdmi_chmap.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/sound/hda/hdmi_chmap.c
+++ b/sound/hda/hdmi_chmap.c
@@ -746,7 +746,7 @@ static int hdmi_chmap_ctl_get(struct snd
 	memset(pcm_chmap, 0, sizeof(pcm_chmap));
 	chmap->ops.get_chmap(chmap->hdac, pcm_idx, pcm_chmap);
 
-	for (i = 0; i < sizeof(chmap); i++)
+	for (i = 0; i < ARRAY_SIZE(pcm_chmap); i++)
 		ucontrol->value.integer.value[i] = pcm_chmap[i];
 
 	return 0;