net: scm: introduce and use scm_recv_unix helper

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Recently, our friends from bluetooth subsystem reported [1] that after
commit 5e2ff6704a ("scm: add SO_PASSPIDFD and SCM_PIDFD") scm_recv()
helper become unusable in kernel modules (because it uses unexported
pidfd_prepare() API).

We were aware of this issue and workarounded it in a hard way
by commit 97154bcf4d ("af_unix: Kconfig: make CONFIG_UNIX bool").

But recently a new functionality was added in the scope of commit
817efd3cad74 ("Bluetooth: hci_sock: Forward credentials to monitor")
and after that bluetooth can't be compiled as a kernel module.

After some discussion in [1] we decided to split scm_recv() into
two helpers, one won't support SCM_PIDFD (used for unix sockets),
and another one will be completely the same as it was before commit
5e2ff6704a ("scm: add SO_PASSPIDFD and SCM_PIDFD").

Link: https://lore.kernel.org/lkml/CAJqdLrpFcga4n7wxBhsFqPQiN8PKFVr6U10fKcJ9W7AcZn+o6Q@mail.gmail.com/ [1]
Fixes: 5e2ff6704a ("scm: add SO_PASSPIDFD and SCM_PIDFD")
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20230627174314.67688-3-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

...

This commit is contained in:

Alexander Mikhalitsyn 2023-06-27 10:43:14 -07:00 • committed by Jakub Kicinski

parent 603fc57ab7

commit a9c49cc2f5

2 changed files with 27 additions and 12 deletions

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include/net/scm.h

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