Re: [PATCH] fsck: avoid looking at NULL blob->object

From: Martin Ågren <martin.agren@gmail.com>
Date: Jun 9, 2018, 13:44 UTC
Message-ID: <CAN0heSqkcZ5KBpaq7R45A7wPxQ3F=6PKeHqwAQztdJyz31Vdwg@mail.gmail.com>
In-Reply-To: <20180609092135.GC6817@sigill.intra.peff.net>

On 9 June 2018 at 11:21, Jeff King <peff@peff.net> wrote:

Show 14 quoted lines

> On Sat, Jun 09, 2018 at 10:50:36AM +0200, Martin Ågren wrote:
>
>> On 9 June 2018 at 10:32, Jeff King <peff@peff.net> wrote:
>> > Except it _does_ do one non-trivial thing, which is call the
>> > report() function, which wants us to pass a pointer to a
>> > "struct object". Which we don't have (we have only a "struct
>> > object_id"). So we erroneously passed the NULL object, which
>>
>> s/passed/dereferenced/? Probably doesn't affect the fix though.
>
> Well, we passed it, and then that function dereferenced it. :)
>
> I'm going to re-roll for the minor bits that Eric pointed out, so I'll
> try to word this better.

My bad. I somehow thought we get into trouble already before we call `report()`. Well, we do, since we have undefined behavior. But for all practical purposes `&blob->object` and `blob` are the same (NULL-)pointer so we only crash after we call `report()`.

Anyway, obviously no need to do anything about this in a v3.

Martin