notes: avoid potential use-after-free during insertion

The note_tree_insert() function may free the leaf_node struct we pass in
(e.g., if it's a duplicate, or if it needs to be combined with an
existing note).

Most callers are happy with this, as they assume that ownership of the
struct is handed off. But in load_subtree(), if we see an error we'll
use the handed-off struct's key_oid to generate the die() message,
potentially accessing freed memory.

We can easily fix this by instead using the original oid that we copied
into the leaf_node struct.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/notes.c b/notes.c
index 3130add61815b2abab35ba0b3f1e5413e5c15d14..9533a14a13394d988e96e38c44163b4f71768ab7 100644 (file)
--- a/notes.c
+++ b/notes.c
@@ -460,7 +460,7 @@ static void load_subtree(struct notes_tree *t, struct leaf_node *subtree,
                        die("Failed to load %s %s into notes tree "
                            "from %s",
                            type == PTR_TYPE_NOTE ? "note" : "subtree",
-                           oid_to_hex(&l->key_oid), t->ref);
+                           oid_to_hex(&object_oid), t->ref);
 
                continue;