linux-kernel - Re: [PATCH] proc: Track /proc/$pid/attr/ opener mm

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Message-ID: <20210609064008.liz2gvpjtyqwx6qr@wittgenstein>
Date:   Wed, 9 Jun 2021 08:40:08 +0200
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrea Righi <andrea.righi@...onical.com>,
        stable@...r.kernel.org, linux-kernel@...r.kernel.org,
        regressions@...ts.linux.dev
Subject: Re: [PATCH] proc: Track /proc/$pid/attr/ opener mm_struct

On Tue, Jun 08, 2021 at 10:12:21AM -0700, Kees Cook wrote:
> Commit bfb819ea20ce ("proc: Check /proc/$pid/attr/ writes against file opener")
> tried to make sure that there could not be a confusion between the opener of
> a /proc/$pid/attr/ file and the writer. It used struct cred to make sure
> the privileges didn't change. However, there were existing cases where a more
> privileged thread was passing the opened fd to a differently privileged thread
> (during container setup). Instead, use mm_struct to track whether the opener
> and writer are still the same process. (This is what several other proc files
> already do, though for different reasons.)
> 
> Reported-by: Christian Brauner <christian.brauner@...ntu.com>
> Reported-by: Andrea Righi <andrea.righi@...onical.com>
> Tested-by: Andrea Righi <andrea.righi@...onical.com>
> Fixes: bfb819ea20ce ("proc: Check /proc/$pid/attr/ writes against file opener")
> Cc: stable@...r.kernel.org
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---

Thanks!
Acked-by: Christian Brauner <christian.brauner@...ntu.com>