linux-kernel - Re: [PATCH v2 0/2] implement OA2_INHERIT

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Message-ID: <08d4dde6-d333-4992-abc6-35291a44c65f@yandex.ru>
Date: Thu, 25 Apr 2024 14:02:40 +0300
From: stsp <stsp2@...dex.ru>
To: Andy Lutomirski <luto@...capital.net>
Cc: linux-kernel@...r.kernel.org, Stefan Metzmacher <metze@...ba.org>,
 Eric Biederman <ebiederm@...ssion.com>,
 Alexander Viro <viro@...iv.linux.org.uk>, Andy Lutomirski <luto@...nel.org>,
 Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
 Jeff Layton <jlayton@...nel.org>, Chuck Lever <chuck.lever@...cle.com>,
 Alexander Aring <alex.aring@...il.com>, linux-fsdevel@...r.kernel.org,
 linux-api@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
 Christian Göttsche <cgzones@...glemail.com>,
 Aleksa Sarai <cyphar@...har.com>
Subject: Re: [PATCH v2 0/2] implement OA2_INHERIT_CRED flag for openat2()

25.04.2024 03:43, Andy Lutomirski пишет:
> But you missed the FMODE_CRED part!

OK, I thought its not needed if fd
is limited to the one created by the
same process. But your explanation
is quite clear on that its needed anyway,
or otherwise the unsuspecting process
doesn't fully drop his privs.
Thank you for explaining that bit.
Which leaves just one question: is
such an opt-in enough or not?
Viro points it may not be enough,
but doesn't explain why exactly.

Maybe we need such an opt-in, and
it should be dropped on exec() and
on passing via unix fd? I don't know
what additional restrictions are needed,
as Viro didn't clarify that part, but the
opt-in is needed for sure.