Patch "USB: gadgetfs: fix checks of wTotalLength in config descriptors" has been added to the 4.9-stable tree

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

USB: gadgetfs: fix checks of wTotalLength in config descriptors

to the 4.9-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:
usb-gadgetfs-fix-checks-of-wtotallength-in-config-descriptors.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Alan Stern <[email protected]>
Date: Fri, 9 Dec 2016 15:24:24 -0500
Subject: USB: gadgetfs: fix checks of wTotalLength in config descriptors

From: Alan Stern <[email protected]>

commit 1c069b057dcf64fada952eaa868d35f02bb0cfc2 upstream.

Andrey Konovalov's fuzz testing of gadgetfs showed that we should improve the driver's checks for valid configuration descriptors passed in by the user. In particular, the driver needs to verify that the wTotalLength value in the descriptor is not too short (smaller than USB_DT_CONFIG_SIZE). And the check for whether wTotalLength is too large has to be changed, because the driver assumes there is always enough room remaining in the buffer to hold a device descriptor (at least USB_DT_DEVICE_SIZE bytes).

This patch adds the additional check and fixes the existing check. It may do a little more than strictly necessary, but one extra check won't hurt.

---
 drivers/usb/gadget/legacy/inode.c |   10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

@@ -1734,10 +1734,12 @@ static struct usb_gadget_driver gadgetfs
  * such as configuration notifications.
  */
 
-static int is_valid_config (struct usb_config_descriptor *config)
+static int is_valid_config(struct usb_config_descriptor *config,
+		unsigned int total)
 {
 	return config->bDescriptorType == USB_DT_CONFIG
 		&& config->bLength == USB_DT_CONFIG_SIZE
+		&& total >= USB_DT_CONFIG_SIZE
 		&& config->bConfigurationValue != 0
 		&& (config->bmAttributes & USB_CONFIG_ATT_ONE) != 0
 		&& (config->bmAttributes & USB_CONFIG_ATT_WAKEUP) == 0;

@@ -1787,7 +1789,8 @@ dev_config (struct file *fd, const char
 	/* full or low speed config */
 	dev->config = (void *) kbuf;
 	total = le16_to_cpu(dev->config->wTotalLength);
-	if (!is_valid_config (dev->config) || total >= length)
+	if (!is_valid_config(dev->config, total) ||
+			total > length - USB_DT_DEVICE_SIZE)
 		goto fail;
 	kbuf += total;
 	length -= total;

@@ -1796,7 +1799,8 @@ dev_config (struct file *fd, const char
 	if (kbuf [1] == USB_DT_CONFIG) {
 		dev->hs_config = (void *) kbuf;
 		total = le16_to_cpu(dev->hs_config->wTotalLength);
-		if (!is_valid_config (dev->hs_config) || total >= length)
+		if (!is_valid_config(dev->hs_config, total) ||
+				total > length - USB_DT_DEVICE_SIZE)
 			goto fail;
 		kbuf += total;
 		length -= total;

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/usb-dummy-hcd-fix-bug-in-stop_activity-handle-ep0.patch queue-4.9/usb-gadgetfs-fix-use-after-free-bug.patch queue-4.9/usb-gadgetfs-fix-checks-of-wtotallength-in-config-descriptors.patch queue-4.9/usb-fix-problems-with-duplicate-endpoint-addresses.patch queue-4.9/usb-gadgetfs-fix-unbounded-memory-allocation-bug.patch