From: Derrick Stolee <derrickstolee@github.com>
To: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Cc: git@vger.kernel.org, Junio C Hamano <gitster@pobox.com>,
Bagas Sanjaya <bagasdotme@gmail.com>
Subject: Re: [PATCH] pack-objects: lazily set up "struct rev_info", don't leak
Date: Mon, 28 Mar 2022 10:04:23 -0400 [thread overview]
Message-ID: <6511a6b4-79da-ffe8-8000-982018a7e701@github.com> (raw)
In-Reply-To: <220326.865yo1leay.gmgdl@evledraar.gmail.com>
On 3/25/2022 8:52 PM, Ævar Arnfjörð Bjarmason wrote:
>
> On Fri, Mar 25 2022, Derrick Stolee wrote:
>
>> On 3/25/2022 1:34 PM, Ævar Arnfjörð Bjarmason wrote:>>> - list_objects_filter_copy(&revs.filter, &filter_options);
>>> + /* attach our CLI --filter to rev_info's filter */
>>> + memcpy(&revs.filter, filter, sizeof(*filter));
>>> + memset(filter, 0, sizeof(*filter));
>>
>> Here, you are removing a deep copy with a shallow copy. After this,
>> freeing the arrays within revs.filter would cause a double-free when
>> freeing the arrays in the original filter_options.
>
> Yes, and that's what we want, right? I.e. we don't want a copy, but to
> use the &filter for parse_options(), then once that's populated we
> shallow-copy that to "struct rev_info"'s "filter", and forget about our
> own copy (i.e. the memset there is redundant, but just a "let's not use
> this again) marker.
>
> Of course this will leak now, but once merged with my
> release_revisions() patch will work, and we'll free what we allocated
> (once!).
>> Even if you fix the deep/shallow copy above, you still need to
>> clean up the filter in two places.
>
> If you "fix" the shallow copying you need to free it twice, but if you
> don't you free it once.
>
> I.e. this is conceptually the same as strbuf_detach() + strbuf_attach().
>
> But maybe I'm missing something...
>
> (If I am it's rather worrying that it passed all our tests, both in your
> series + merged with the release_revisions() series).
My problem is that you need to know that the filter data was
"detached" in a different scope than it is defined.
* filter_options is defined in cmd_pack_objects()
* The detach and reattach to revs is in get_object_list()
Your model requires internal information from get_object_list()
to know that you shouldn't release filter_options within
cmd_pack_objects(), which I think is a code smell. Better to
have something allocated in cmd_pack_objects() be freed in that
same method so it is visually detectable that we are freeing
correctly.
Thanks,
-Stolee
next prev parent reply other threads:[~2022-03-28 14:04 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-22 17:28 [PATCH 0/5] Partial bundle follow ups Derrick Stolee via GitGitGadget
2022-03-22 17:28 ` [PATCH 1/5] list-objects-filter: remove CL_ARG__FILTER Derrick Stolee via GitGitGadget
2022-03-22 17:28 ` [PATCH 2/5] pack-objects: move revs out of get_object_list() Derrick Stolee via GitGitGadget
2022-03-22 17:28 ` [PATCH 3/5] pack-objects: parse --filter directly into revs.filter Derrick Stolee via GitGitGadget
2022-03-22 19:37 ` [-SPAM-] " Ramsay Jones
2022-03-23 13:48 ` Derrick Stolee
2022-03-22 21:15 ` Ævar Arnfjörð Bjarmason
2022-03-22 17:28 ` [PATCH 4/5] bundle: move capabilities to end of 'verify' Derrick Stolee via GitGitGadget
2022-03-23 7:08 ` Bagas Sanjaya
2022-03-23 13:39 ` Derrick Stolee
2022-03-22 17:28 ` [PATCH 5/5] bundle: output hash information in 'verify' Derrick Stolee via GitGitGadget
2022-03-23 21:27 ` [PATCH 0/5] Partial bundle follow ups Junio C Hamano
2022-03-25 14:25 ` [PATCH] pack-objects: lazily set up "struct rev_info", don't leak Ævar Arnfjörð Bjarmason
2022-03-25 14:57 ` Derrick Stolee
2022-03-25 16:00 ` Ævar Arnfjörð Bjarmason
2022-03-25 16:41 ` Derrick Stolee
2022-03-25 17:34 ` Ævar Arnfjörð Bjarmason
2022-03-25 19:08 ` Derrick Stolee
2022-03-26 0:52 ` Ævar Arnfjörð Bjarmason
2022-03-28 14:04 ` Derrick Stolee [this message]
2022-03-25 18:53 ` Junio C Hamano
2022-03-26 1:09 ` Ævar Arnfjörð Bjarmason
2022-03-28 15:43 ` [PATCH v2] " Ævar Arnfjörð Bjarmason
2022-03-28 15:58 ` Derrick Stolee
2022-03-28 17:10 ` Junio C Hamano
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