From: Mathias Payer <mathias.payer@nebelwelt.net>
Date: Wed, 5 Dec 2018 21:19:59 +0100
Subject: USB: check usb_get_extra_descriptor for proper size
Git-commit: 704620afc70cf47abb9d6a1a57f3825d2bca49cf
Patch-mainline: v4.20-rc6
References: bsc#1119714 CVE-2018-20169

When reading an extra descriptor, we need to properly check the minimum
and maximum size allowed, to prevent from invalid data being sent by a
device.

Reported-by: Hui Peng <benquike@gmail.com>
Reported-by: Mathias Payer <mathias.payer@nebelwelt.net>
Co-developed-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Hui Peng <benquike@gmail.com>
Signed-off-by: Mathias Payer <mathias.payer@nebelwelt.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
---
 drivers/usb/core/hub.c    |    2 +-
 drivers/usb/core/usb.c    |    6 +++---
 drivers/usb/host/hwa-hc.c |    2 +-
 include/linux/usb.h       |    4 ++--
 4 files changed, 7 insertions(+), 7 deletions(-)

--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -2227,7 +2227,7 @@ static int usb_enumerate_device_otg(stru
 		/* descriptor may appear anywhere in config */
 		err = __usb_get_extra_descriptor(udev->rawdescriptors[0],
 				le16_to_cpu(udev->config[0].desc.wTotalLength),
-				USB_DT_OTG, (void **) &desc);
+				USB_DT_OTG, (void **) &desc, sizeof(*desc));
 		if (err || !(desc->bmAttributes & USB_OTG_HNP))
 			return 0;
 
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -833,14 +833,14 @@ EXPORT_SYMBOL_GPL(usb_get_current_frame_
  */
 
 int __usb_get_extra_descriptor(char *buffer, unsigned size,
-			       unsigned char type, void **ptr)
+			       unsigned char type, void **ptr, size_t minsize)
 {
 	struct usb_descriptor_header *header;
 
 	while (size >= sizeof(struct usb_descriptor_header)) {
 		header = (struct usb_descriptor_header *)buffer;
 
-		if (header->bLength < 2) {
+		if (header->bLength < 2 || header->bLength > size) {
 			printk(KERN_ERR
 				"%s: bogus descriptor, type %d length %d\n",
 				usbcore_name,
@@ -849,7 +849,7 @@ int __usb_get_extra_descriptor(char *buf
 			return -1;
 		}
 
-		if (header->bDescriptorType == type) {
+		if (header->bDescriptorType == type && header->bLength >= minsize) {
 			*ptr = header;
 			return 0;
 		}
--- a/drivers/usb/host/hwa-hc.c
+++ b/drivers/usb/host/hwa-hc.c
@@ -654,7 +654,7 @@ static int hwahc_security_create(struct
 	top = itr + itr_size;
 	result = __usb_get_extra_descriptor(usb_dev->rawdescriptors[index],
 			le16_to_cpu(usb_dev->actconfig->desc.wTotalLength),
-			USB_DT_SECURITY, (void **) &secd);
+			USB_DT_SECURITY, (void **) &secd, sizeof(*secd));
 	if (result == -1) {
 		dev_warn(dev, "BUG? WUSB host has no security descriptors\n");
 		return 0;
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -406,11 +406,11 @@ struct usb_host_bos {
 };
 
 int __usb_get_extra_descriptor(char *buffer, unsigned size,
-	unsigned char type, void **ptr);
+	unsigned char type, void **ptr, size_t min);
 #define usb_get_extra_descriptor(ifpoint, type, ptr) \
 				__usb_get_extra_descriptor((ifpoint)->extra, \
 				(ifpoint)->extralen, \
-				type, (void **)ptr)
+				type, (void **)ptr, sizeof(**(ptr)))
 
 /* ----------------------------------------------------------------------- */