[RFC PATCH 0/3] coredump, net: fix layer violation with direct connection

[John Ericson]

From: John Ericson <mail at JohnEricson.me>

In https://lore.kernel.org/all/akWxrjOl4Up02Bvq@pop-os.localdomain/ Cong
Wang asked about doing things without new syscalls for my fd-based
connect idea. This got me investigating a few things, all of which I hope to
submit as patches.

This is the first one. I stumbled on `SOCK_COREDUMP` in `af_unix.c`, and
I realized that this was --- right in the part of the kernel I was
already looking at --- an excellent example of something that directly
connecting to a socket could do better. This is not because the
filesystem would never be involved (the interface in procfs still
specifies a path) but because the core dumper wants to resolve that path
differently than the usual way.

The first two commits are refactors that expose/create the necessary
functionality, and then the last commit actually does the untangling of
the unix socket implementation and the core dumper. See especially that
third commit message for details.

I hope this is a compelling use-case for you all, that does not touch
the UABI yet, but also does just the sort of thing that would be nice to
expose with a new syscall.

John

John Ericson (3):
  af_unix: factor out unix_lookup_bsd_path()
  af_unix: factor out kernel_unix_connect_direct()
  coredump, net: remove `SOCK_COREDUMP`

 fs/coredump.c                 |  47 +++--
 include/linux/lsm_hook_defs.h |   3 +-
 include/linux/net.h           |   1 -
 include/linux/security.h      |   4 +-
 include/net/af_unix.h         |   2 +
 net/unix/af_unix.c            | 335 +++++++++++++++++++++++++---------
 security/landlock/fs.c        |   7 +-
 security/security.c           |   5 +-
 8 files changed, 287 insertions(+), 117 deletions(-)

-- 
2.54.0