linux-hardening - Re: [PATCH] exec: Check __FMODE_EXEC instead of in

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Message-ID: <62d1c43c-18e5-4ddf-ad85-c47e5c58d79a@I-love.SAKURA.ne.jp>
Date: Thu, 25 Jan 2024 23:34:00 +0900
From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To: Kees Cook <keescook@...omium.org>, Jann Horn <jannh@...gle.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
        Josh Triplett <josh@...htriplett.org>,
        Kevin Locke <kevin@...inlocke.name>,
        John Johansen <john.johansen@...onical.com>,
        Paul Moore
 <paul@...l-moore.com>, James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Kentaro Takeda
 <takedakn@...data.co.jp>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
        Eric Biederman <ebiederm@...ssion.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        apparmor@...ts.ubuntu.com, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] exec: Check __FMODE_EXEC instead of in_execve for LSMs

On 2024/01/25 6:50, Kees Cook wrote:
> Yeah, I was just noticing this. I was over thinking. :) It does look
> like all that is needed is to remove __FMODE_EXEC.

I worry that some out-of-tree kernel code continues using __FMODE_EXEC for
opening for non-execve() purpose. If that happened, TOMOYO will be fooled...
Can't we remove __FMODE_EXEC and FMODE_EXEC flag from f_flags instead of
replacing current->in_execve with file->f_flags & __FMODE_EXEC ?