Re: [PATCH] object-name: reject too-deep recursive ancestor queries

From: Junio C Hamano <gitster@pobox.com>
Date: Nov 24, 2023, 09:44 UTC
Message-ID: <xmqqy1en7af2.fsf@gitster.g>
In-Reply-To: <ZV9Za7iCL6WiE-Py@tanuki>

Patrick Steinhardt <ps@pks.im> writes:

> I have to wonder whether we should tighten restrictions even further:
> instead of manually keeping track of how deep in the stack we are, we
> limit the length of revisions to at most 1MB. I would claim that this
> limit is sufficiently large to never be a problem in practice.

Tempting.

> Revisions
> are limited to 4kB on most platforms anyway due to the maximum path
> length.

I do not quite get this part, though.

When we get "HEAD~~~~~~~~~^2~~~~~~" from the user, do we somehow try to create a file or a directory with that name and fail due to ENAMETOOLONG?

There are ways like "git rev-list --stdin" to cause Git read input lines of arbitrary length, so I do not think the command line length limit does not come into the picture, either.

But I do agree that the only useful use of such a revision string that is longer than 1MB would be to attack.