Re: [PATCH v2 00/10] net: support thread-specific pidfds for send and connect

[Alexander Mikhalitsyn]

Am Mi., 9. Sept. 2026 um 12:43 Uhr schrieb Christian Brauner
<brauner@xxxxxxxxxx>:
>
> SO_PASSPIDFD/SCM_PIDFD and SO_PEERPIDFD allow to retrieve a pidfd for
> the thread-group leader. The coredump server using the coredump socket
> cannot get a handle on the task that took the signal and is writing the
> coredump easily. Workloads interested in per-thread authentification
> have similar problems.
>
> Add SO_PASSPIDFD_THREAD and SO_PEERPIDFD_THREAD. We record the sending
> and the connecting thread in addition to the thread-group leader.
>
> SO_PASSPIDFD_THREAD functions like SO_PASSPIDFD but instead of an
> SCM_PIDFD message for the thread-group leader, SCM_PIDFD sends a pidfd
> for the specific thread. SO_PASSPIDFD_THREAD is mutually exclusive with
> SO_PASSPIDFD. The last one set takes precedence and disables the other
> one. Both SO_PASSCRED and SO_PASSPIDFD receivers see one writer per
> process as before.
>
> SO_PEERPIDFD_THREAD allows to retrieve a pidfd for the specific thread
> that called connect(), listen(), or socketpair().
>
> pidfs_coredump() now also stamps the dumping thread's struct pid so a
> pidfd for that thread reports the coredump like the pidfd of the
> thread-group leader does.
>
> Signed-off-by: Christian Brauner (Amutable) <brauner@xxxxxxxxxx>

Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@xxxxxxxxxxxxxx>

> ---
> Changes in v2:
> - Fix a few documentation issues.
> - Link to v1: https://patch.msgid.link/20260831-work-unix-passpidfd-v1-0-70cbfda0c7ba@xxxxxxxxxx
>
> ---
> Christian Brauner (10):
>       pid: add helpers to operate on a struct pid array
>       af_unix: record the pid of the sending thread
>       net: add SO_PASSPIDFD_THREAD to get a thread-specific SCM_PIDFD
>       selftests/net: SO_PASSPIDFD_THREAD
>       net: turn sk_peer_pid into an array indexed by pid type
>       af_unix: record the pid of the connecting thread
>       net: add SO_PEERPIDFD_THREAD to get a thread-specific pidfd
>       selftests/net: SO_PEERPIDFD_THREAD
>       pidfs: record the coredump on the dumping thread's pid too
>       selftests/coredump: check the dumping thread's pidfd
>
>  arch/alpha/include/uapi/asm/socket.h               |   4 +
>  arch/mips/include/uapi/asm/socket.h                |   4 +
>  arch/parisc/include/uapi/asm/socket.h              |   4 +
>  arch/sparc/include/uapi/asm/socket.h               |   4 +
>  fs/coredump.c                                      |  22 +-
>  fs/pidfs.c                                         |  27 +-
>  include/linux/coredump.h                           |   4 +-
>  include/linux/pid.h                                |  53 +++
>  include/linux/pid_types.h                          |   8 +
>  include/linux/pidfs.h                              |   5 +
>  include/linux/sched/signal.h                       |  18 +
>  include/net/scm.h                                  |   7 +-
>  include/net/sock.h                                 |  14 +-
>  include/trace/events/landlock.h                    |   2 +-
>  include/uapi/asm-generic/socket.h                  |   4 +
>  net/bluetooth/af_bluetooth.c                       |   6 +-
>  net/bluetooth/hci_sock.c                           |   8 +-
>  net/bluetooth/l2cap_sock.c                         |   2 +-
>  net/core/scm.c                                     |  36 +-
>  net/core/sock.c                                    | 120 ++++---
>  net/unix/af_unix.c                                 |  67 ++--
>  net/unix/af_unix.h                                 |   3 +-
>  tools/lib/python/kdoc/xforms_lists.py              |   1 +
>  .../selftests/coredump/coredump_socket_test.c      | 175 ++++++++++
>  tools/testing/selftests/coredump/coredump_test.h   |   2 +
>  .../selftests/coredump/coredump_test_helpers.c     |  49 +++
>  tools/testing/selftests/net/af_unix/Makefile       |   2 +
>  tools/testing/selftests/net/af_unix/scm_pidfd.c    | 366 +++++++++++++++++++++
>  28 files changed, 907 insertions(+), 110 deletions(-)
> ---
> base-commit: cee9395acd8043be0644b25c34bfa86623f2b935
> change-id: 20260825-work-unix-passpidfd-086a1ec09e8a
>