USB: fix bug in initialization of interface minor numbers

Recent changes in the usbhid layer exposed a bug in usbcore.  If
CONFIG_USB_DYNAMIC_MINORS is enabled then an interface may be assigned
a minor number of 0.  However interfaces that aren't registered as USB
class devices also have their minor number set to 0, during
initialization.  As a result usb_find_interface() may return the
wrong interface, leading to a crash.

This patch (as1418) fixes the problem by initializing every
interface's minor number to -1.  It also cleans up the
usb_register_dev() function, which besides being somewhat awkwardly
written, does not unwind completely on all its error paths.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Tested-by: Philip J. Turmel <philip@turmel.org>
Tested-by: Gabriel Craciunescu <nix.or.die@googlemail.com>
Tested-by: Alex Riesen <raa.lkml@gmail.com>
Tested-by: Matthias Bayer <jackdachef@gmail.com>
CC: Jiri Kosina <jkosina@suse.cz>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 17 insertions, 19 deletions

diff --git a/drivers/usb/core/file.c b/drivers/usb/core/file.c
index f06f5dbc8cdc..1e6ccef2cf0c 100644
--- a/drivers/usb/core/file.c
+++ b/drivers/usb/core/file.c
@@ -159,9 +159,9 @@ void usb_major_cleanup(void)
 int usb_register_dev(struct usb_interface *intf,
                      struct usb_class_driver *class_driver)
 {
-        int retval = -EINVAL;
+        int retval;
         int minor_base = class_driver->minor_base;
-        int minor = 0;
+        int minor;
         char name[20];
         char *temp;
 
@@ -173,12 +173,17 @@ int usb_register_dev(struct usb_interface *intf,
          */
         minor_base = 0;
 #endif
-        intf->minor = -1;
-
-        dbg ("looking for a minor, starting at %d", minor_base);
 
         if (class_driver->fops == NULL)
-                goto exit;
+                return -EINVAL;
+        if (intf->minor >= 0)
+                return -EADDRINUSE;
+
+        retval = init_usb_class();
+        if (retval)
+                return retval;
+
+        dev_dbg(&intf->dev, "looking for a minor, starting at %d", minor_base);
 
         down_write(&minor_rwsem);
         for (minor = minor_base; minor < MAX_USB_MINORS; ++minor) {
@@ -186,20 +191,12 @@ int usb_register_dev(struct usb_interface *intf,
                         continue;
 
                 usb_minors[minor] = class_driver->fops;
-
-                retval = 0;
+                intf->minor = minor;
                 break;
         }
         up_write(&minor_rwsem);
-
-        if (retval)
-                goto exit;
-
-        retval = init_usb_class();
-        if (retval)
-                goto exit;
-
-        intf->minor = minor;
+        if (intf->minor < 0)
+                return -EXFULL;
 
         /* create a usb class device for this usb interface */
         snprintf(name, sizeof(name), class_driver->name, minor - minor_base);
@@ -213,11 +210,11 @@ int usb_register_dev(struct usb_interface *intf,
                                       "%s", temp);
         if (IS_ERR(intf->usb_dev)) {
                 down_write(&minor_rwsem);
-                usb_minors[intf->minor] = NULL;
+                usb_minors[minor] = NULL;
+                intf->minor = -1;
                 up_write(&minor_rwsem);
                 retval = PTR_ERR(intf->usb_dev);
         }
-exit:
         return retval;
 }
 EXPORT_SYMBOL_GPL(usb_register_dev);
diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
index 844683e50383..9f0ce7de0e36 100644
--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -1802,6 +1802,7 @@ free_interfaces:
                 intf->dev.groups = usb_interface_groups;
                 intf->dev.dma_mask = dev->dev.dma_mask;
                 INIT_WORK(&intf->reset_ws, __usb_queue_reset_device);
+                intf->minor = -1;
                 device_initialize(&intf->dev);
                 dev_set_name(&intf->dev, "%d-%s:%d.%d",
                         dev->bus->busnum, dev->devpath,