From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: Junio C Hamano <gitster@pobox.com>
Cc: git@vger.kernel.org, Bagas Sanjaya <bagasdotme@gmail.com>,
Emily Shaffer <emilyshaffer@google.com>
Subject: Re: [PATCH 2/2] hooks: fix a TOCTOU in "did we run a hook?" heuristic
Date: Sat, 19 Feb 2022 05:48:42 +0100 [thread overview]
Message-ID: <220219.864k4vfo75.gmgdl@evledraar.gmail.com> (raw)
In-Reply-To: <xmqq4k4vyata.fsf@gitster.g>
On Fri, Feb 18 2022, Junio C Hamano wrote:
>> -int run_commit_hook(int editor_is_used, const char *index_file, const char *name, ...);
>> +int run_commit_hook(int editor_is_used, const char *index_file,
>> + int *invoked_hook, const char *name, ...);
>>
>
> Even though my gut feeling tells me that turning the "yes/no"
> integer into an enum that includes "there was no such hook", "I
> tried to run it, but it failed to run" [*], "I ran it and it was
> happy". would be a more viable approach for the longer term, I
> guess this extra and ad-hoc parameter would be sufficient as a
> shorter term improvement.
>
> Side note: optionally "failed to run" may be split into "failed
> to even start (e.g. ENOEXEC)" and "started successfully but
> exited with non-zero status". There may or may not be callers
> that wants to see them as distinct cases right now, but an
> interface based on returned enum value would be easier to extend
> than having to add a pointer to return variable every time we
> need to know more details.
Yes, I debated with myself whether I should add some more generic
interface to it, and decided just to do the bare minumum of adding
something the "struct run_hooks_opt".
FWIW the "yes/no" is not that, run_commit_hook() just returns the value
of run_hooks_opt(), which is currently either an <0 error, or the status
code from the hook. I.e. what gets passed to the "task_finished_fn"
callback for run_processes_parallel_tr2(). I.e. the finish_command()
return value.
We do cover the "ENOEXEC" case in ignoring it, since if we fail on
startup we won't say we ran the hook.
I think in practice what'll matter is this "invoked_hook". I.e. if we
failed to parse our config, the hook wasn't executable or whatever
that's just a <0 error, and we didn't run the hook.
Or, if we ran it at all (even if it failed) we'll know that we need to
e.g. discard_index(), since we can't guarantee that the hook didn't get
that far that we'll need to update our own assumptions.
A caller who ares about anything else will also need to deal with a lot
more complexity once we have config-based-hooks / parallel hooks by
default. I.e. was that ENOEXEC one of N hooks, all of them, did all/one
exit non-zero etc?
Whereas "int *invoked_hook" we can just set as long as we invoked any of
them at all.
next prev parent reply other threads:[~2022-02-19 4:58 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-18 20:43 [PATCH 0/2] hooks: fix a race in hook execution Ævar Arnfjörð Bjarmason
2022-02-18 20:43 ` [PATCH 1/2] merge: don't run post-hook logic on --no-verify Ævar Arnfjörð Bjarmason
2022-02-18 23:57 ` Junio C Hamano
2022-02-18 20:43 ` [PATCH 2/2] hooks: fix a TOCTOU in "did we run a hook?" heuristic Ævar Arnfjörð Bjarmason
2022-02-19 0:11 ` Junio C Hamano
2022-02-19 4:48 ` Ævar Arnfjörð Bjarmason [this message]
2022-02-19 4:08 ` Taylor Blau
2022-02-19 10:46 ` Ævar Arnfjörð Bjarmason
2022-03-07 12:33 ` [PATCH v2 0/2] hooks: fix a race in hook execution Ævar Arnfjörð Bjarmason
2022-03-07 12:33 ` [PATCH v2 1/2] merge: don't run post-hook logic on --no-verify Ævar Arnfjörð Bjarmason
2022-03-07 12:33 ` [PATCH v2 2/2] hooks: fix an obscure TOCTOU "did we just run a hook?" race Ævar Arnfjörð Bjarmason
2022-03-21 20:30 ` Jonathan Tan
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