[PATCH] Chardev checking of overlapping ranges

[linux-2.6-block.git] / fs / char_dev.c

diff --git a/fs/char_dev.c b/fs/char_dev.c
index 0009346d827f52ad2da3c24bdbb6485d5cdfa6dd..33b95af89da4471482816ff97b701e7c5743761c 100644 (file)
--- a/fs/char_dev.c
+++ b/fs/char_dev.c
@@ -128,13 +128,31 @@ __register_chrdev_region(unsigned int major, unsigned int baseminor,
 
        for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
                if ((*cp)->major > major ||
-                   ((*cp)->major == major && (*cp)->baseminor >= baseminor))
+                   ((*cp)->major == major &&
+                    (((*cp)->baseminor >= baseminor) ||
+                     ((*cp)->baseminor + (*cp)->minorct > baseminor))))
                        break;
-       if (*cp && (*cp)->major == major &&
-           (*cp)->baseminor < baseminor + minorct) {
-               ret = -EBUSY;
-               goto out;
+
+       /* Check for overlapping minor ranges.  */
+       if (*cp && (*cp)->major == major) {
+               int old_min = (*cp)->baseminor;
+               int old_max = (*cp)->baseminor + (*cp)->minorct - 1;
+               int new_min = baseminor;
+               int new_max = baseminor + minorct - 1;
+
+               /* New driver overlaps from the left.  */
+               if (new_max >= old_min && new_max <= old_max) {
+                       ret = -EBUSY;
+                       goto out;
+               }
+
+               /* New driver overlaps from the right.  */
+               if (new_min <= old_max && new_min >= old_min) {
+                       ret = -EBUSY;
+                       goto out;
+               }
        }
+
        cd->next = *cp;
        *cp = cd;
        mutex_unlock(&chrdevs_lock);