orangefs: Fix the size of a memory allocation in orangefs_bufmap_alloc()

'buffer_index_array' really looks like a bitmap. So it should be allocated
as such.
When kzalloc is called, a number of bytes is expected, but a number of
longs is passed instead.

In get(), if not enough memory is allocated, un-allocated memory may be
read or written.

So use bitmap_zalloc() to safely allocate the correct memory size and
avoid un-expected behavior.

While at it, change the corresponding kfree() into bitmap_free() to keep
the semantic.

Fixes: ea2c9c9 ("orangefs: bufmap rewrite")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Mike Marshall <hubcap@omnibond.com>

fs/orangefs/orangefs-bufmap.c

@@ -176,7 +176,7 @@ orangefs_bufmap_free(struct orangefs_bufmap *bufmap)
 {
 	kfree(bufmap->page_array);
 	kfree(bufmap->desc_array);
-	kfree(bufmap->buffer_index_array);
+	bitmap_free(bufmap->buffer_index_array);
 	kfree(bufmap);
 }
 
@@ -226,8 +226,7 @@ orangefs_bufmap_alloc(struct ORANGEFS_dev_map_desc *user_desc)
 	bufmap->desc_size = user_desc->size;
 	bufmap->desc_shift = ilog2(bufmap->desc_size);
 
-	bufmap->buffer_index_array =
-		kzalloc(DIV_ROUND_UP(bufmap->desc_count, BITS_PER_LONG), GFP_KERNEL);
+	bufmap->buffer_index_array = bitmap_zalloc(bufmap->desc_count, GFP_KERNEL);
 	if (!bufmap->buffer_index_array)
 		goto out_free_bufmap;
 
@@ -250,7 +249,7 @@ orangefs_bufmap_alloc(struct ORANGEFS_dev_map_desc *user_desc)
 out_free_desc_array:
 	kfree(bufmap->desc_array);
 out_free_index_array:
-	kfree(bufmap->buffer_index_array);
+	bitmap_free(bufmap->buffer_index_array);
 out_free_bufmap:
 	kfree(bufmap);
 out: