From: ZheNing Hu <adlternative@gmail.com>
To: Junio C Hamano <gitster@pobox.com>
Cc: ZheNing Hu via GitGitGadget <gitgitgadget@gmail.com>,
Git List <git@vger.kernel.org>,
Johannes Schindelin <Johannes.Schindelin@gmx.de>
Subject: Re: [PATCH v4] [GSOC] ref-filter: fix read invalid union member bug
Date: Tue, 11 May 2021 14:28:32 +0800 [thread overview]
Message-ID: <CAOLTT8QR4Ga41ADKhgB4=C7VgGbJEe5G5HSbcjRb51H2yQVRPA@mail.gmail.com> (raw)
In-Reply-To: <xmqqcztyovf7.fsf@gitster.g>
Junio C Hamano <gitster@pobox.com> 于2021年5月11日周二 上午10:29写道:
>
> "ZheNing Hu via GitGitGadget" <gitgitgadget@gmail.com> writes:
>
> > Change from last version:
> > Prove that the bug may appear when using %(color) atom. And add
> > corresponding test for it.
>
> > ++test_expect_success '%(color:#aa22ac) must success' '
>
> s/success/succeed/
>
> But more importantly, I am not sure how this is supposed to
> demonstrate existing breakage around the %(push). Did you mean to
> use %(push) instead of %(refname) or something?
>
Ah, I don’t think this scene of damage is related to using %(push)
or %(refname).
We are just in the process of using `populate_value()`, if the atom we
specify meets the following conditions, then the condition of
atom->u.remote_ref.push!=0 will be established.
1. The atom that triggers the bug , its "if" condition order must after
"if (atom->u.remote_ref.push)", such as %(refname) or %(worktreepath),
they can be executed correctly because their order is before "push".
2. The member size in used_atom.u corresponding to the atom must
larger than 17 bytes, because the offset of "u.remote_ref.push" in
"u.remote_ref" is 17, the satisfied atoms are only "%(color)" and
"%(contents)", their corresponding members are u.color and u.contents.
3. We happen to be able to fill in the 17th position of these structures,
which makes atom->u.remote_ref.push not equal to 0 established.
So this kind of bug is not related to %(push), an atom that satisfies
the above conditions will make `if (atom->u.remote_ref.push)` be true.
then execute the program logic related to `%(push)`.
Now, we only have `%(color)` can trigger it "sometime",
It is unpredictable to fill in the 17th byte of used_atom.u.color,
so we cannot track all the atoms related to this bug.
git for-each-ref --format="%(color:#aa22ac)%(refname)"
git for-each-ref --format="%(color:#aa22ad)%(refname)"
will trigger the bug.
git for-each-ref --format="%(color:#aa22ae)%(refname)"
git for-each-ref --format="%(color:#aa22af)%(refname)"
will not trigger the bug.
In other words, we cannot use a perfect test set to cover all broken.
So now `%(color:#aa22ac)` is enough for explain the problem of this bug.
Thanks.
--
ZheNing Hu
next prev parent reply other threads:[~2021-05-11 6:28 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-05 15:31 [PATCH] [GSOC] ref-filter: solve bugs caused by enumeration ZheNing Hu via GitGitGadget
2021-05-06 1:53 ` Junio C Hamano
2021-05-06 5:02 ` ZheNing Hu
2021-05-06 5:35 ` Junio C Hamano
2021-05-06 10:39 ` ZheNing Hu
2021-05-06 11:20 ` Junio C Hamano
2021-05-06 11:52 ` ZheNing Hu
2021-05-06 21:20 ` Junio C Hamano
2021-05-07 4:32 ` ZheNing Hu
2021-05-07 4:49 ` Junio C Hamano
2021-05-07 5:09 ` ZheNing Hu
2021-05-06 16:31 ` [PATCH v2] [GSOC] ref-filter: fix read invalid union member bug ZheNing Hu via GitGitGadget
2021-05-08 15:26 ` [PATCH v3] " ZheNing Hu via GitGitGadget
2021-05-10 7:21 ` Junio C Hamano
2021-05-10 12:35 ` ZheNing Hu
2021-05-10 7:27 ` Junio C Hamano
2021-05-10 12:51 ` ZheNing Hu
2021-05-10 15:01 ` [PATCH v4] " ZheNing Hu via GitGitGadget
2021-05-11 2:29 ` Junio C Hamano
2021-05-11 6:28 ` ZheNing Hu [this message]
2021-05-11 9:30 ` Junio C Hamano
2021-05-11 11:47 ` ZheNing Hu
2021-05-11 13:12 ` Junio C Hamano
2021-05-11 13:31 ` ZheNing Hu
2021-05-11 15:35 ` [PATCH v5] " ZheNing Hu via GitGitGadget
2021-05-12 1:36 ` Junio C Hamano
2021-05-12 10:37 ` ZheNing Hu
2021-05-12 12:12 ` [PATCH v6] " ZheNing Hu via GitGitGadget
2021-05-12 23:24 ` Junio C Hamano
2021-05-13 9:29 ` ZheNing Hu
2021-05-13 15:13 ` [PATCH v7] " ZheNing Hu via GitGitGadget
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