selinux: import NetLabel category bitmaps correctly

The existing ebitmap_netlbl_import() code didn't correctly handle the
case where the ebitmap_node was not aligned/sized to a power of two,
this patch fixes this (on x86_64 ebitmap_node contains six bitmaps
making a range of 0..383).
Signed-off-by: Paul Moore <paul@paul-moore.com>

security/selinux/ss/ebitmap.c

@@ -165,7 +165,7 @@ int ebitmap_netlbl_import(struct ebitmap *ebmap,
 			e_iter = kzalloc(sizeof(*e_iter), GFP_ATOMIC);
 			if (e_iter == NULL)
 				goto netlbl_import_failure;
-			e_iter->startbit = offset & ~(EBITMAP_SIZE - 1);
+			e_iter->startbit = offset - (offset % EBITMAP_SIZE);
 			if (e_prev == NULL)
 				ebmap->node = e_iter;
 			else