Re: [PATCH 04/33] notes: make get_note return pointer to struct object_id

["René Scharfe" <l.s.r@web.de>]

Am 30.05.2017 um 19:30 schrieb Brandon Williams:
> @@ -392,7 +392,7 @@ static int add(int argc, const char **argv, const char *prefix)
>   	const char *object_ref;
>   	struct notes_tree *t;
>   	unsigned char object[20], new_note[20];
> -	const unsigned char *note;
> +	const struct object_id *note;
>   	struct note_data d = { 0, 0, NULL, STRBUF_INIT };
>   	struct option options[] = {
>   		{ OPTION_CALLBACK, 'm', "message", &d, N_("message"),

In between here, note can be set to NULL...

> @@ -453,7 +453,7 @@ static int add(int argc, const char **argv, const char *prefix)
>   			sha1_to_hex(object));
>   	}
>   
> -	prepare_note_data(object, &d, note);
> +	prepare_note_data(object, &d, note->hash);

... which we then dereference here.

> @@ -598,13 +598,13 @@ static int append_edit(int argc, const char **argv, const char *prefix)
>   	t = init_notes_check(argv[0], NOTES_INIT_WRITABLE);
>   	note = get_note(t, object);
>   
> -	prepare_note_data(object, &d, edit ? note : NULL);
> +	prepare_note_data(object, &d, edit && note ? note->hash : NULL);

Here a NULL check was added; we need a similar one above as well.

-- >8 --
Subject: [PATCH] notes: don't access hash of NULL object_id pointer

Check if note is NULL, as we already do for different purposes a few
lines above, and pass a NULL pointer to prepare_note_data() in that
case instead of trying to access the hash member.

Found with Clang's UBSan.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
---
The third parameter of prepare_note_data() could easily be turned into
an object_id pointer (and it should), but this patch is meant to be a
minimal fix.

 builtin/notes.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/builtin/notes.c b/builtin/notes.c
index 77573cf1ea..4303848e04 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -456,7 +456,7 @@ static int add(int argc, const char **argv, const char *prefix)
 			oid_to_hex(&object));
 	}
 
-	prepare_note_data(&object, &d, note->hash);
+	prepare_note_data(&object, &d, note ? note->hash : NULL);
 	if (d.buf.len || allow_empty) {
 		write_note_data(&d, new_note.hash);
 		if (add_note(t, &object, &new_note, combine_notes_overwrite))
-- 
2.13.3