linux-kernel - [PATCH 5.4 125/388] ALSA: usb-audio: Dont create a mixer element with bogus volume range

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Message-Id: <20200929110016.517001947@linuxfoundation.org>
Date:   Tue, 29 Sep 2020 12:57:36 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Takashi Iwai <tiwai@...e.de>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 125/388] ALSA: usb-audio: Dont create a mixer element with bogus volume range

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

[ Upstream commit e9a0ef0b5ddcbc0d56c65aefc0f18d16e6f71207 ]

Some USB-audio descriptors provide a bogus volume range (e.g. volume
min and max are identical), which confuses user-space.
This patch makes the driver skipping such a control element.

BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=206221
Link: https://lore.kernel.org/r/20200214144928.23628-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 sound/usb/mixer.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index 9079c380228fc..8aa96ed0b1b56 100644
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -1684,6 +1684,16 @@ static void __build_feature_ctl(struct usb_mixer_interface *mixer,
 	/* get min/max values */
 	get_min_max_with_quirks(cval, 0, kctl);
 
+	/* skip a bogus volume range */
+	if (cval->max <= cval->min) {
+		usb_audio_dbg(mixer->chip,
+			      "[%d] FU [%s] skipped due to invalid volume\n",
+			      cval->head.id, kctl->id.name);
+		snd_ctl_free_one(kctl);
+		return;
+	}
+
+
 	if (control == UAC_FU_VOLUME) {
 		check_mapped_dB(map, cval);
 		if (cval->dBmin < cval->dBmax || !cval->initialized) {
-- 
2.25.1