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From:   Sasha Levin <sashal@kernel.org>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc:     Takashi Iwai <tiwai@suse.de>, Sasha Levin <sashal@kernel.org>,
        alsa-devel@alsa-project.org
Subject: [PATCH AUTOSEL 5.4 131/330] ALSA: usb-audio: Don't create a mixer element with bogus volume range
Date:   Thu, 17 Sep 2020 21:57:51 -0400
Message-Id: <20200918020110.2063155-131-sashal@kernel.org>
In-Reply-To: <20200918020110.2063155-1-sashal@kernel.org>
References: <20200918020110.2063155-1-sashal@kernel.org>
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From: Takashi Iwai <tiwai@suse.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@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.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