[PATCH 0/6] open in-tree files with O_NOFOLLOW

[Jeff King <peff@peff.net>]

On Tue, Feb 16, 2021 at 07:48:23AM -0500, Jeff King wrote:

> I am beginning to wonder if just opening them all with O_NOFOLLOW (and a
> hacky 2-syscall fallback for portability) might be less ugly than all of
> this.

So here's what that series might look like. It would replace all of this
verify_path() stuff entirely (and fsck, though we might want to add
detection to fsck just as an informational thing). It gives similar
protections, and would similarly force people using an in-tree symlink
to stop doing that. But it makes it much less of a pain to do so,
because they can still check out, etc; the symlinks just won't be
followed.

I think we could even use the same technique to roll back the
restrictions on .gitmodules being a symlink. That one makes me a bit
more nervous, just because we also write it. I _think_ that might be
safe, because we only do so using a temp file and rename(), which should
replace the symlink.

  [1/6]: add open_nofollow() helper
  [2/6]: attr: convert "macro_ok" into a flags field
  [3/6]: exclude: add flags parameter to add_patterns()
  [4/6]: attr: do not respect symlinks for in-tree .gitattributes
  [5/6]: exclude: do not respect symlinks for in-tree .gitignore
  [6/6]: mailmap: do not respect symlinks for in-tree .mailmap

 attr.c                    | 60 +++++++++++++++++++++++++--------------
 builtin/sparse-checkout.c |  8 +++---
 dir.c                     | 21 ++++++++++----
 dir.h                     |  3 +-
 git-compat-util.h         |  7 +++++
 mailmap.c                 | 22 ++++++++++----
 t/t0003-attributes.sh     | 36 +++++++++++++++++++++--
 t/t0008-ignores.sh        | 34 ++++++++++++++++++++++
 t/t4203-mailmap.sh        | 31 ++++++++++++++++++++
 wrapper.c                 | 16 +++++++++++
 10 files changed, 197 insertions(+), 41 deletions(-)

-Peff