linux-kernel - Re: [6.8-rc1 Regression] Unable to exec apparmor

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Date: Thu, 25 Jan 2024 09:17:32 -0800
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc: Kees Cook <keescook@...omium.org>, John Johansen <john.johansen@...onical.com>, 
	Paul Moore <paul@...l-moore.com>, Kevin Locke <kevin@...inlocke.name>, 
	Josh Triplett <josh@...htriplett.org>, Mateusz Guzik <mjguzik@...il.com>, 
	Al Viro <viro@...iv.linux.org.uk>, linux-mm@...ck.org, linux-fsdevel@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org, 
	Kentaro Takeda <takedakn@...data.co.jp>
Subject: Re: [6.8-rc1 Regression] Unable to exec apparmor_parser from virt-aa-helper

On Thu, 25 Jan 2024 at 06:17, Tetsuo Handa
<penguin-kernel@...ove.sakura.ne.jp> wrote:
>
> On 2024/01/25 3:27, Linus Torvalds wrote:
> > The whole cred use of current->in_execve in tomoyo should
> > *also* be fixed, but I didn't even try to follow what it actually
> > wanted.
>
> Due to TOMOYO's unique domain transition (transits to new domain before
> execve() succeeds and returns to old domain if execve() failed), TOMOYO
> depends on a tricky ordering shown below.

Ok, that doesn't really clarify anything for me.

I'm less interested in what the call paths are, and more like "_Why_
is all this needed for tomoyo?"

Why doesn't tomoyo just install the new cred at "commit_creds()" time?

(The security hooks that surround that  are
"->bprm_committing_creds()" and "->bprm_committed_creds()")

IOW, the whole "save things across two *independent* execve() calls"
seems crazy.

Very strange and confusing.

                    Linus