From 3763f6186703d9939913996da1c71d8f8ddb035c Mon Sep 17 00:00:00 2001
From: Jorge Sanjuan <jorge.sanjuan@codethink.co.uk>
Date: Fri, 4 May 2018 04:24:01 +0300
Subject: [PATCH] ALSA: usb: Only get AudioControl header for UAC1 class.
Git-commit: 3763f6186703d9939913996da1c71d8f8ddb035c
Patch-mainline: v4.18-rc1
References: bsc#1121278

The control header needs to be read from buffer at this point only
in the case of UAC1 protocol. Move it inside the switch case as other
protocols such as the Basic Audio Device spec will have an empty buffer
that is latter filled as inferred.

Signed-off-by: Jorge Sanjuan <jorge.sanjuan@codethink.co.uk>
[ruslan: updated with recently added sanity checks]
Signed-off-by: Ruslan Bilovol <ruslan.bilovol@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

---
 sound/usb/card.c | 39 +++++++++++++++++++--------------------
 1 file changed, 19 insertions(+), 20 deletions(-)

diff --git a/sound/usb/card.c b/sound/usb/card.c
index 36c289bae169..0d7a5d70634e 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -221,32 +221,13 @@ static int snd_usb_create_streams(struct snd_usb_audio *chip, int ctrlif)
 	struct usb_device *dev = chip->dev;
 	struct usb_host_interface *host_iface;
 	struct usb_interface_descriptor *altsd;
-	void *control_header;
 	int i, protocol;
-	int rest_bytes;
 
 	/* find audiocontrol interface */
 	host_iface = &usb_ifnum_to_if(dev, ctrlif)->altsetting[0];
-	control_header = snd_usb_find_csint_desc(host_iface->extra,
-						 host_iface->extralen,
-						 NULL, UAC_HEADER);
 	altsd = get_iface_desc(host_iface);
 	protocol = altsd->bInterfaceProtocol;
 
-	if (!control_header) {
-		dev_err(&dev->dev, "cannot find UAC_HEADER\n");
-		return -EINVAL;
-	}
-
-	rest_bytes = (void *)(host_iface->extra + host_iface->extralen) -
-		control_header;
-
-	/* just to be sure -- this shouldn't hit at all */
-	if (rest_bytes <= 0) {
-		dev_err(&dev->dev, "invalid control header\n");
-		return -EINVAL;
-	}
-
 	switch (protocol) {
 	default:
 		dev_warn(&dev->dev,
@@ -255,7 +236,25 @@ static int snd_usb_create_streams(struct snd_usb_audio *chip, int ctrlif)
 		/* fall through */
 
 	case UAC_VERSION_1: {
-		struct uac1_ac_header_descriptor *h1 = control_header;
+		struct uac1_ac_header_descriptor *h1;
+		int rest_bytes;
+
+		h1 = snd_usb_find_csint_desc(host_iface->extra,
+							 host_iface->extralen,
+							 NULL, UAC_HEADER);
+		if (!h1) {
+			dev_err(&dev->dev, "cannot find UAC_HEADER\n");
+			return -EINVAL;
+		}
+
+		rest_bytes = (void *)(host_iface->extra +
+				host_iface->extralen) - (void *)h1;
+
+		/* just to be sure -- this shouldn't hit at all */
+		if (rest_bytes <= 0) {
+			dev_err(&dev->dev, "invalid control header\n");
+			return -EINVAL;
+		}
 
 		if (rest_bytes < sizeof(*h1)) {
 			dev_err(&dev->dev, "too short v1 buffer descriptor\n");
-- 
2.20.1