Re: [PATCH] Don't dereference NULL upon lookup_tree failure.

> Jim Meyering <jim@meyering.net> writes:
>
>> Junio C Hamano <gitster@pobox.com> wrote:
>> ...
>>> Sorry, I asked for a wrong thing.  parse_object() reads and
>>> finds out the type, so type there is presumably the right type
>>> of the object (which is OBJ_TREE).  Then parse_object_buffer()
>>> checks if it has already seen the object of the same SHA-1 and
>>> finds that somebody had earlier told that SHA-1 name is of a
>>> commit object.  Either you found a SHA-1 collision (highly
>>> unlikely) or the earlier caller had lied.  And I think what
>>> really needs to be fixed is that lying caller.  That is not in
>>> the above call chain.
>>
>> I presume that parsecvs is the culprit, in constructing
>> an invalid repository...
>
> Independent of who creates a "invalid repository", our tools
> should be prepared to be fed bad data and not get upset.
> Somebody in our code read a non-commit (or it did not read
> anything) and told the object layer it is a commit.  That
> codepath needs to be tightened up, no?