Re: [PATCH net-next v3] af_unix: pass pidfd flags via SCM_PIDFD cmsg

[Kuniyuki Iwashima]

From: Stas Sergeev <stsp2@xxxxxxxxx>
Date: Sat, 16 Nov 2024 13:11:20 +0300
> Currently SCM_PIDFD cmsg cannot be sent via unix socket
> (returns -EINVAL) and SO_PASSPIDFD doesn't support flags.
> The created pidfd always has flags set to 0.
> 
> This patch implements SCM_PIDFD cmsg in AF_UNIX socket, which
> can be used to send flags to SO_PASSPIDFD-enabled recipient.
> 
> Self-test is added for the propagation of PIDFD_NONBLOCK flag.
> 
> This is mainly needed for the future extensions, like eg this one:
> https://lore.kernel.org/lkml/8288a08e-448b-43c2-82dc-59f87d0d9072@xxxxxxxxx/T/#me1237e46deba8574b77834b7704e63559ffef9cb
> where it was suggested to try solving the supplementary groups
> problem with pidfd.
> 
> Changes in v3: specify target tree in patch subject

It seems you missed other feedback, especially __scm_recv_common()
needs a small change.

net-next is closed during the merge window for v6.13-rc1, so please
post v4 after Dec 2nd.
https://lore.kernel.org/netdev/20241118071654.695bb1a2@xxxxxxxxxx/