linux-kernel - Re: [PATCH resend] seccomp: Make duplicate listener detection non-racy

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Message-Id: <160193704489.2698420.14892403272288554518.b4-ty@chromium.org>
Date:   Mon,  5 Oct 2020 15:30:54 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Jann Horn <jannh@...gle.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Tycho Andersen <tycho@...ho.pizza>,
        Andy Lutomirski <luto@...capital.net>,
        Will Drewry <wad@...omium.org>, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH resend] seccomp: Make duplicate listener detection non-racy

On Mon, 5 Oct 2020 03:44:01 +0200, Jann Horn wrote:
> Currently, init_listener() tries to prevent adding a filter with
> SECCOMP_FILTER_FLAG_NEW_LISTENER if one of the existing filters already
> has a listener. However, this check happens without holding any lock that
> would prevent another thread from concurrently installing a new filter
> (potentially with a listener) on top of the ones we already have.
> 
> Theoretically, this is also a data race: The plain load from
> current->seccomp.filter can race with concurrent writes to the same
> location.
> 
> [...]

Applied, thanks!

I added the stable CC, but I'd agree: it's not so urgent that I need to
get this into Linus's tree ahead of the regular merge window. :)

[1/1] seccomp: Make duplicate listener detection non-racy
      https://git.kernel.org/kees/c/ed2d479d3335

-- 
Kees Cook