usb: Avoid possible out-of-bound accesses caused by malicious devices

The maximum number of configurations and interfaces are fixed but there is
no out-of-bound checking to prevent a malicious USB device to report large
values for these and cause accesses outside the arrays' memory.

Fixes: CVE-2020-25647
Reported-by: Joseph Tartaro <joseph.tartaro@ioactive.com>
Reported-by: Ilja Van Sprundel <ivansprundel@ioactive.com>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

diff --git a/grub-core/bus/usb/usb.c b/grub-core/bus/usb/usb.c
index 8da5e4c7491b55df25c01e420700f7d76b583051..7cb3cc230b2364108dd10fea31ceef3f5cab7fb0 100644 (file)
--- a/grub-core/bus/usb/usb.c
+++ b/grub-core/bus/usb/usb.c
@@ -75,6 +75,9 @@ grub_usb_controller_iterate (grub_usb_controller_iterate_hook_t hook,
 grub_usb_err_t
 grub_usb_clear_halt (grub_usb_device_t dev, int endpoint)
 {
+  if (endpoint >= GRUB_USB_MAX_TOGGLE)
+    return GRUB_USB_ERR_BADDEVICE;
+
   dev->toggle[endpoint] = 0;
   return grub_usb_control_msg (dev, (GRUB_USB_REQTYPE_OUT
                                     | GRUB_USB_REQTYPE_STANDARD
@@ -134,10 +137,10 @@ grub_usb_device_initialize (grub_usb_device_t dev)
     return err;
   descdev = &dev->descdev;
 
-  for (i = 0; i < 8; i++)
+  for (i = 0; i < GRUB_USB_MAX_CONF; i++)
     dev->config[i].descconf = NULL;
 
-  if (descdev->configcnt == 0)
+  if (descdev->configcnt == 0 || descdev->configcnt > GRUB_USB_MAX_CONF)
     {
       err = GRUB_USB_ERR_BADDEVICE;
       goto fail;
@@ -172,6 +175,12 @@ grub_usb_device_initialize (grub_usb_device_t dev)
       /* Skip the configuration descriptor.  */
       pos = dev->config[i].descconf->length;
 
+      if (dev->config[i].descconf->numif > GRUB_USB_MAX_IF)
+        {
+          err = GRUB_USB_ERR_BADDEVICE;
+          goto fail;
+        }
+
       /* Read all interfaces.  */
       for (currif = 0; currif < dev->config[i].descconf->numif; currif++)
        {
@@ -217,7 +226,7 @@ grub_usb_device_initialize (grub_usb_device_t dev)
 
  fail:
 
-  for (i = 0; i < 8; i++)
+  for (i = 0; i < GRUB_USB_MAX_CONF; i++)
     grub_free (dev->config[i].descconf);
 
   return err;

diff --git a/include/grub/usb.h b/include/grub/usb.h
index 512ae1dd0e64931c852847c9d52efdbd6b2caccb..6475c552fc6d4ad6e278c448b335d618097170e7 100644 (file)
--- a/include/grub/usb.h
+++ b/include/grub/usb.h
@@ -23,6 +23,10 @@
 #include <grub/usbdesc.h>
 #include <grub/usbtrans.h>
 
+#define GRUB_USB_MAX_CONF    8
+#define GRUB_USB_MAX_IF      32
+#define GRUB_USB_MAX_TOGGLE  256
+
 typedef struct grub_usb_device *grub_usb_device_t;
 typedef struct grub_usb_controller *grub_usb_controller_t;
 typedef struct grub_usb_controller_dev *grub_usb_controller_dev_t;
@@ -167,7 +171,7 @@ struct grub_usb_configuration
   struct grub_usb_desc_config *descconf;
 
   /* Interfaces associated to this configuration.  */
-  struct grub_usb_interface interf[32];
+  struct grub_usb_interface interf[GRUB_USB_MAX_IF];
 };
 
 struct grub_usb_hub_port
@@ -191,7 +195,7 @@ struct grub_usb_device
   struct grub_usb_controller controller;
 
   /* Device configurations (after opening the device).  */
-  struct grub_usb_configuration config[8];
+  struct grub_usb_configuration config[GRUB_USB_MAX_CONF];
 
   /* Device address.  */
   int addr;
@@ -203,7 +207,7 @@ struct grub_usb_device
   int initialized;
 
   /* Data toggle values (used for bulk transfers only).  */
-  int toggle[256];
+  int toggle[GRUB_USB_MAX_TOGGLE];
 
   /* Used by libusb wrapper.  Schedulded for removal. */
   void *data;