Re: t5702 failing under ASan on master

From: brian m. carlson <sandals@crustytoothpaste.net>
Date: Jan 30, 2019, 11:40 UTC
Message-ID: <20190130114016.GD24387@genre.crustytoothpaste.net>
In-Reply-To: <CACsJy8AVoETLkB5rLft27Rz7V9xPFN9fk=8g9-fCR61fVi4vjw@mail.gmail.com>

On Wed, Jan 30, 2019 at 05:07:20PM +0700, Duy Nguyen wrote:

Show 6 quoted lines

> If I understand ASan report correctly alternate_shallow_file memory is
> already gone after the first fetch, when we update the shallow file.
> But we're doing two fetches in the same process (the tag backfill
> thingy), the second fetch reuses the dangling alternate_shallow_file
> pointer and ASan caught it. Resetting the variable seems like the
> right way to go.

Ah, I think I was missing the fact that we're doing a tag backfill. That explains a lot.

Show 8 quoted lines

> But should we reset it to an empty string? We would pass
> "--shallow-file=" to "git index-pack", which is treated as "no shallow
> file" (i.e. complete repo). This sounds wrong because this is still a
> shallow repository.
> 
> I suppose setting alternate_shallow_file to NULL would be ok. "git
> index-pack" will just go back to reading $GIT_DIR/info/shallow, which
> has been updated and contains correct info.

Yeah, that sounds like a better choice. I'll send a complete patch which does this.

> PS. No idea how ASan blames your series for this. Yeah maybe memory
> layout and stuff. But it does spot a real problem.

I don't doubt this is a problem. We'll definitely want to fix it before the release, since if I see it in development, somebody will likely see it in production.

-- 
brian m. carlson: Houston, Texas, US
OpenPGP: https://keybase.io/bk2204