linux-kernel - Re: [PATCH v6 0/3] implement OA2_CRED

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Message-ID: <5b5cc31f-a5be-4f64-a97b-7708466ace82@yandex.ru>
Date: Tue, 7 May 2024 12:02:10 +0300
From: stsp <stsp2@...dex.ru>
To: Aleksa Sarai <cyphar@...har.com>
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>,
 David Laight <David.Laight@...lab.com>, linux-fsdevel@...r.kernel.org,
 linux-api@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
 Christian Göttsche <cgzones@...glemail.com>
Subject: Re: [PATCH v6 0/3] implement OA2_CRED_INHERIT flag for openat2()

07.05.2024 10:50, Aleksa Sarai пишет:
> If you are a privileged process which plans to change users,

Not privileged at all.
But I think what you say is still possible
with userns?


> A new attack I just thought of while writing this mail is that because
> there is no RESOLVE_NO_XDEV requirement, it should be possible for the
> process to get an arbitrary write primitive by creating a new
> userns+mountns and then bind-mounting / underneath the directory.
Doesn't this need a write perm to a
directory? In his case this is not a threat,
because you are not supposed to have a
write perm to that dir. OA2_CRED_INHERIT
is the only way to write.