hfs: do not free node before using

hfs_bmap_free() frees the node via hfs_bnode_put(node).  However, it
then reads node->this when dumping error message on an error path, which
may result in a use-after-free bug.  This patch frees the node only when
it is never again used.

Link: http://lkml.kernel.org/r/[email protected]
Fixes: a1185ffa2fc ("HFS rewrite")
Signed-off-by: Pan Bian <[email protected]>
Reviewed-by: Andrew Morton <[email protected]>
Cc: Joe Perches <[email protected]>
Cc: Ernesto A. Fernandez <[email protected]>
Cc: Viacheslav Dubeyko <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

fs/hfs/btree.c

@@ -338,13 +338,14 @@ void hfs_bmap_free(struct hfs_bnode *node)
 
 		nidx -= len * 8;
 		i = node->next;
-		hfs_bnode_put(node);
 		if (!i) {
 			/* panic */;
 			pr_crit("unable to free bnode %u. bmap not found!\n",
 				node->this);
+			hfs_bnode_put(node);
 			return;
 		}
+		hfs_bnode_put(node);
 		node = hfs_bnode_find(tree, i);
 		if (IS_ERR(node))
 			return;