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From: Junio C Hamano <gitster@pobox.com>
To: Jeff King <peff@peff.net>
Cc: Taylor Blau <me@ttaylorr.com>, git@vger.kernel.org, stolee@gmail.com
Subject: Re: [PATCH 3/3] commit-graph.c: handle corrupt/missing trees
Date: Fri, 06 Sep 2019 10:11:09 -0700	[thread overview]
Message-ID: <xmqq5zm5nydu.fsf@gitster-ct.c.googlers.com> (raw)
In-Reply-To: <xmqqo8zxnz0m.fsf@gitster-ct.c.googlers.com> (Junio C. Hamano's message of "Fri, 06 Sep 2019 09:57:29 -0700")

Junio C Hamano <gitster@pobox.com> writes:

> ...
> Is there even a single caller that is prepared to react to NULL?
>
>     Answer. There is a single hit inside fsck.c that wants to report
>     an error without killing ourselves in fsck_commit_buffer().  I
>     however doubt its use of get_commit_tree() is correct in the
>     first place.  The function is about validating the commit object
>     payload manually, without trusting the result of parse_commit(),
>     and it does read the object name of the tree object; the call to
>     get_commit_tree() used for reporting the error there should
>     probably become has_object() on the tree_oid.

At least we need to ensure, not just has_object(), but the object
indeed claims to be a tree object.  It is OK if it is a corrupt
tree object---we'll catch its brokenness separately anyway.

    Hmm, the should we also tolerate the pointed object to be broken
    in a way that it is not even able to claim to be a tree object?
    That would mean that has_object() is sufficient to check here.

OK, so... 

> So, after fixing the above, we may safely be able to die inside
> get_commit_tree() instead of returning NULL.
>
> By the way, I think get_commit_tree() and parse_commit() in fsck
> should always use the value obtained from the underlying object and
> bypass any caches like commit graph---if they pay attention to the
> caches, they should be fixed.  Secondary caches like commit graph
> should of course be validated against what are recorded in the
> underlying object, but that should be done separately.

  reply	other threads:[~2019-09-06 17:11 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-05 22:04 [PATCH 0/3] commit-graph: harden against various corruptions Taylor Blau
2019-09-05 22:04 ` [PATCH 1/3] t/t5318: introduce failing 'git commit-graph write' tests Taylor Blau
2019-09-06 16:48   ` Derrick Stolee
2019-09-05 22:04 ` [PATCH 2/3] commit-graph.c: handle commit parsing errors Taylor Blau
2019-09-05 22:04 ` [PATCH 3/3] commit-graph.c: handle corrupt/missing trees Taylor Blau
2019-09-06  6:19   ` Jeff King
2019-09-06 15:42     ` Taylor Blau
2019-09-06 17:34       ` Jeff King
2019-09-06 16:51     ` Derrick Stolee
2019-09-06 17:37       ` Jeff King
2019-09-06 16:57     ` Junio C Hamano
2019-09-06 17:11       ` Junio C Hamano [this message]
2019-09-06 17:30         ` Jeff King
2019-09-06 17:28       ` Jeff King
2019-09-09 17:55         ` Junio C Hamano

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