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

[Brandon Williams <bmwill@google.com>]

On 07/15, René Scharfe wrote:
> 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.

Looks good, thanks for catching this!

> 
> 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

-- 
Brandon Williams