[PATCH 5.10.y] ALSA: usb-audio: Fix a DMA to stack memory bug

["Benoît Sevens" <bsevens@google.com>]

From: Dan Carpenter <dan.carpenter@linaro.org>

The usb_get_descriptor() function does DMA so we're not allowed
to use a stack buffer for that.  Doing DMA to the stack is not portable
all architectures.  Move the "new_device_descriptor" from being stored
on the stack and allocate it with kmalloc() instead.

Fixes: b909df18ce2a ("ALSA: usb-audio: Fix potential out-of-bound accesses for Extigy and Mbox devices")
Cc: stable@kernel.org
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://patch.msgid.link/60e3aa09-039d-46d2-934c-6f123026c2eb@stanley.mountain
Signed-off-by: Takashi Iwai <tiwai@suse.de>
(cherry picked from commit f7d306b47a24367302bd4fe846854e07752ffcd9)
[Benoît: there is no mbox3 suppport and no __free macro in 5.15]
Signed-off-by: Benoît Sevens <bsevens@google.com>
---
 sound/usb/quirks.c | 31 +++++++++++++++++++++----------
 1 file changed, 21 insertions(+), 10 deletions(-)

diff --git a/sound/usb/quirks.c b/sound/usb/quirks.c
index 9590c16501ef..eed155f12a1f 100644
--- a/sound/usb/quirks.c
+++ b/sound/usb/quirks.c
@@ -595,7 +595,7 @@ int snd_usb_create_quirk(struct snd_usb_audio *chip,
 static int snd_usb_extigy_boot_quirk(struct usb_device *dev, struct usb_interface *intf)
 {
 	struct usb_host_config *config = dev->actconfig;
-	struct usb_device_descriptor new_device_descriptor;
+	struct usb_device_descriptor *new_device_descriptor = NULL;
 	int err;
 
 	if (le16_to_cpu(get_cfg_desc(config)->wTotalLength) == EXTIGY_FIRMWARE_SIZE_OLD ||
@@ -606,15 +606,20 @@ static int snd_usb_extigy_boot_quirk(struct usb_device *dev, struct usb_interfac
 				      0x10, 0x43, 0x0001, 0x000a, NULL, 0);
 		if (err < 0)
 			dev_dbg(&dev->dev, "error sending boot message: %d\n", err);
+
+		new_device_descriptor = kmalloc(sizeof(*new_device_descriptor), GFP_KERNEL);
+		if (!new_device_descriptor)
+			return -ENOMEM;
 		err = usb_get_descriptor(dev, USB_DT_DEVICE, 0,
-				&new_device_descriptor, sizeof(new_device_descriptor));
+				new_device_descriptor, sizeof(*new_device_descriptor));
 		if (err < 0)
 			dev_dbg(&dev->dev, "error usb_get_descriptor: %d\n", err);
-		if (new_device_descriptor.bNumConfigurations > dev->descriptor.bNumConfigurations)
+		if (new_device_descriptor->bNumConfigurations > dev->descriptor.bNumConfigurations)
 			dev_dbg(&dev->dev, "error too large bNumConfigurations: %d\n",
-				new_device_descriptor.bNumConfigurations);
+				new_device_descriptor->bNumConfigurations);
 		else
-			memcpy(&dev->descriptor, &new_device_descriptor, sizeof(dev->descriptor));
+			memcpy(&dev->descriptor, new_device_descriptor, sizeof(dev->descriptor));
+		kfree(new_device_descriptor);
 		err = usb_reset_configuration(dev);
 		if (err < 0)
 			dev_dbg(&dev->dev, "error usb_reset_configuration: %d\n", err);
@@ -946,7 +951,7 @@ static void mbox2_setup_48_24_magic(struct usb_device *dev)
 static int snd_usb_mbox2_boot_quirk(struct usb_device *dev)
 {
 	struct usb_host_config *config = dev->actconfig;
-	struct usb_device_descriptor new_device_descriptor;
+	struct usb_device_descriptor *new_device_descriptor = NULL;
 	int err;
 	u8 bootresponse[0x12];
 	int fwsize;
@@ -981,15 +986,21 @@ static int snd_usb_mbox2_boot_quirk(struct usb_device *dev)
 
 	dev_dbg(&dev->dev, "device initialised!\n");
 
+	new_device_descriptor = kmalloc(sizeof(*new_device_descriptor), GFP_KERNEL);
+	if (!new_device_descriptor)
+		return -ENOMEM;
+
 	err = usb_get_descriptor(dev, USB_DT_DEVICE, 0,
-		&new_device_descriptor, sizeof(new_device_descriptor));
+		new_device_descriptor, sizeof(*new_device_descriptor));
 	if (err < 0)
 		dev_dbg(&dev->dev, "error usb_get_descriptor: %d\n", err);
-	if (new_device_descriptor.bNumConfigurations > dev->descriptor.bNumConfigurations)
+	if (new_device_descriptor->bNumConfigurations > dev->descriptor.bNumConfigurations)
 		dev_dbg(&dev->dev, "error too large bNumConfigurations: %d\n",
-			new_device_descriptor.bNumConfigurations);
+			new_device_descriptor->bNumConfigurations);
 	else
-		memcpy(&dev->descriptor, &new_device_descriptor, sizeof(dev->descriptor));
+		memcpy(&dev->descriptor, new_device_descriptor, sizeof(dev->descriptor));
+
+	kfree(new_device_descriptor);
 
 	err = usb_reset_configuration(dev);
 	if (err < 0)
-- 
2.47.1.613.gc27f4b7a9f-goog