drivers/char/misc.c: clear allocation bit in minor bitmap when device register fails

If there's a failure creating the device (because there's already one with
the same name, for example), the current implementation does not clear the
bit for the allocated minor and that number is lost for future
allocations.

Second, the test currently in misc_deregister is broken, since it does not
test for the 0 minor.
Signed-off-by: NThadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/char/misc.c

@@ -214,6 +214,9 @@ int misc_register(struct miscdevice * misc)
 	misc->this_device = device_create(misc_class, misc->parent, dev,
 					  misc, "%s", misc->name);
 	if (IS_ERR(misc->this_device)) {
+		int i = misc->minor;
+		if (i < DYNAMIC_MINORS && i >= 0)
+			misc_minors[i>>3] &= ~(1 << (i & 7));
 		err = PTR_ERR(misc->this_device);
 		goto out;
 	}
@@ -248,9 +251,8 @@ int misc_deregister(struct miscdevice *misc)
 	mutex_lock(&misc_mtx);
 	list_del(&misc->list);
 	device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor));
-	if (i < DYNAMIC_MINORS && i>0) {
-		misc_minors[i>>3] &= ~(1 << (misc->minor & 7));
-	}
+	if (i < DYNAMIC_MINORS && i >= 0)
+		misc_minors[i>>3] &= ~(1 << (i & 7));
 	mutex_unlock(&misc_mtx);
 	return 0;
 }