From: Jonathan Tan <firstname.lastname@example.org> To: Taylor Blau <email@example.com> Cc: Jonathan Tan <firstname.lastname@example.org>, email@example.com, firstname.lastname@example.org, email@example.com Subject: Re: [PATCH 2/2] builtin/pack-objects.c: ensure pack validity from MIDX bitmap objects Date: Sun, 15 May 2022 23:11:19 -0700 [thread overview] Message-ID: <firstname.lastname@example.org> (raw) In-Reply-To: <Yn+v8mEHm2sfo4sn@nand.local> Taylor Blau <email@example.com> writes: > On Fri, May 13, 2022 at 04:06:39PM -0700, Jonathan Tan wrote: > > (An alternative to the change in this patch may be to reset *found_pack > > to NULL when it is found that the pack is invalid, but I haven't > > investigated all the callers to see if they can tolerate *found_pack > > moving changing non-NULL to NULL, so the change in this patch is > > probably more practical.) > > I haven't either, but I think that this points out a flaw in the patch I > originally posted. > > Consider this: > > - `want_object_in_pack()` calls `want_found_object()` with a pack that > has gone away and has zero open fds, and `want_found_object()` > returns -1 > - `want_object_in_pack()` continues and calls > `want_object_in_pack_one()` later on, with some pack that is the > same as `*found_pack` > - `want_object_in_pack_one()` then _doesn't_ call `is_pack_valid()` > (since `p == *found_pack`), leaving us in the same situation as > before. > > I think that would be sufficient to hit this race even after this patch. Ah, yes, indeed this would be a problem. > I'll take a look to see if `want_object_in_pack()` callers can handle > `*found_pack` being set back to NULL. They should be able to, but I want > to do a little more careful analysis to be sure. Sounds good. > Thanks for pointing this out, I am so glad for your review! :-) Thanks for your kind words! Thanks for your explanations too.
next prev parent reply other threads:[~2022-05-16 6:11 UTC|newest] Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-05-13 16:23 [PATCH 0/2] pack-objects: fix a pair of MIDX bitmap-related races Taylor Blau 2022-05-13 16:23 ` [PATCH 1/2] pack-bitmap: check preferred pack validity when opening MIDX bitmap Taylor Blau 2022-05-13 18:19 ` Junio C Hamano 2022-05-13 19:55 ` Taylor Blau 2022-05-13 16:23 ` [PATCH 2/2] builtin/pack-objects.c: ensure pack validity from MIDX bitmap objects Taylor Blau 2022-05-13 23:06 ` Jonathan Tan 2022-05-14 13:17 ` Taylor Blau 2022-05-16 6:07 ` Jonathan Tan 2022-05-14 13:34 ` Taylor Blau 2022-05-16 6:11 ` Jonathan Tan [this message] 2022-05-24 18:54 ` [PATCH v2 0/4] pack-objects: fix a pair of MIDX bitmap-related races Taylor Blau 2022-05-24 18:54 ` [PATCH v2 1/4] pack-bitmap.c: check preferred pack validity when opening MIDX bitmap Taylor Blau 2022-05-24 19:36 ` Ævar Arnfjörð Bjarmason 2022-05-24 21:38 ` Taylor Blau 2022-05-24 21:51 ` Ævar Arnfjörð Bjarmason 2022-05-24 18:54 ` [PATCH v2 2/4] builtin/pack-objects.c: avoid redundant NULL check Taylor Blau 2022-05-24 21:44 ` Junio C Hamano 2022-05-25 0:11 ` Taylor Blau 2022-05-24 18:54 ` [PATCH v2 3/4] builtin/pack-objects.c: ensure included `--stdin-packs` exist Taylor Blau 2022-05-24 19:46 ` Ævar Arnfjörð Bjarmason 2022-05-24 21:33 ` Taylor Blau 2022-05-24 21:49 ` Ævar Arnfjörð Bjarmason 2022-05-24 22:03 ` Junio C Hamano 2022-05-25 0:14 ` Taylor Blau 2022-05-26 19:21 ` Victoria Dye 2022-05-26 20:05 ` Taylor Blau 2022-05-24 18:54 ` [PATCH v2 4/4] builtin/pack-objects.c: ensure pack validity from MIDX bitmap objects Taylor Blau 2022-05-24 21:38 ` [PATCH v2 0/4] pack-objects: fix a pair of MIDX bitmap-related races Junio C Hamano 2022-05-25 0:16 ` Taylor Blau
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