Patch "ALSA: usb-audio: Fix the missing ctl name suffix at parsing SU" has been added to the 3.18-stable tree

[<gregkh@linuxfoundation.org>]

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

    ALSA: usb-audio: Fix the missing ctl name suffix at parsing SU

to the 3.18-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-fix-the-missing-ctl-name-suffix-at-parsing-su.patch
and it can be found in the queue-3.18 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 5a15f289ee87eaf33f13f08a4909ec99d837ec5f Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Mon, 18 Dec 2017 23:36:57 +0100
Subject: ALSA: usb-audio: Fix the missing ctl name suffix at parsing SU

From: Takashi Iwai <tiwai@suse.de>

commit 5a15f289ee87eaf33f13f08a4909ec99d837ec5f upstream.

The commit 89b89d121ffc ("ALSA: usb-audio: Add check return value for
usb_string()") added the check of the return value from
snd_usb_copy_string_desc(), which is correct per se, but it introduced
a regression.  In the original code, either the "Clock Source",
"Playback Source" or "Capture Source" suffix is added after the
terminal string, while the commit changed it to add the suffix only
when get_term_name() is failing.  It ended up with an incorrect ctl
name like "PCM" instead of "PCM Capture Source".

Also, even the original code has a similar bug: when the ctl name is
generated from snd_usb_copy_string_desc() for the given iSelector, it
also doesn't put the suffix.

This patch addresses these issues: the suffix is added always when no
static mapping is found.  Also the patch tries to put more comments
and cleans up the if/else block for better readability in order to
avoid the same pitfall again.

Fixes: 89b89d121ffc ("ALSA: usb-audio: Add check return value for usb_string()")
Reported-and-tested-by: Mauro Santos <registo.mailling@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 sound/usb/mixer.c |   27 ++++++++++++++++-----------
 1 file changed, 16 insertions(+), 11 deletions(-)

--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -2094,20 +2094,25 @@ static int parse_audio_selector_unit(str
 	kctl->private_value = (unsigned long)namelist;
 	kctl->private_free = usb_mixer_selector_elem_free;
 
-	nameid = uac_selector_unit_iSelector(desc);
+	/* check the static mapping table at first */
 	len = check_mapped_name(map, kctl->id.name, sizeof(kctl->id.name));
-	if (len)
-		;
-	else if (nameid)
-		len = snd_usb_copy_string_desc(state, nameid, kctl->id.name,
-					 sizeof(kctl->id.name));
-	else
-		len = get_term_name(state, &state->oterm,
-				    kctl->id.name, sizeof(kctl->id.name), 0);
-
 	if (!len) {
-		strlcpy(kctl->id.name, "USB", sizeof(kctl->id.name));
+		/* no mapping ? */
+		/* if iSelector is given, use it */
+		nameid = uac_selector_unit_iSelector(desc);
+		if (nameid)
+			len = snd_usb_copy_string_desc(state, nameid,
+						       kctl->id.name,
+						       sizeof(kctl->id.name));
+		/* ... or pick up the terminal name at next */
+		if (!len)
+			len = get_term_name(state, &state->oterm,
+				    kctl->id.name, sizeof(kctl->id.name), 0);
+		/* ... or use the fixed string "USB" as the last resort */
+		if (!len)
+			strlcpy(kctl->id.name, "USB", sizeof(kctl->id.name));
 
+		/* and add the proper suffix */
 		if (desc->bDescriptorSubtype == UAC2_CLOCK_SELECTOR)
 			append_ctl_name(kctl, " Clock Source");
 		else if ((state->oterm.type & 0xff00) == 0x0100)


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

queue-3.18/alsa-usb-audio-fix-the-missing-ctl-name-suffix-at-parsing-su.patch
queue-3.18/alsa-rawmidi-avoid-racy-info-ioctl-via-ctl-device.patch
queue-3.18/acpi-apei-erst-fix-missing-error-handling-in-erst_reader.patch