linux-kernel - Re: [PATCH v3 3/5] mm: Make PR_MDWE_REFUSE_EXEC

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Date:   Fri, 25 Aug 2023 15:29:58 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Florent Revest <revest@...omium.org>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org, catalin.marinas@....com,
        anshuman.khandual@....com, joey.gouly@....com, mhocko@...e.com,
        david@...hat.com, peterx@...hat.com, izbyshev@...ras.ru,
        broonie@...nel.org, szabolcs.nagy@....com, kpsingh@...nel.org,
        gthelen@...gle.com, toiwoton@...il.com
Subject: Re: [PATCH v3 3/5] mm: Make PR_MDWE_REFUSE_EXEC_GAIN an unsigned long

On Tue, Jul 04, 2023 at 05:36:27PM +0200, Florent Revest wrote:
> Defining a prctl flag as an int is a footgun because on a 64 bit machine
> and with a variadic implementation of prctl (like in musl and glibc),
> when used directly as a prctl argument, it can get casted to long with
> garbage upper bits which would result in unexpected behaviors.
> 
> This patch changes the constant to an unsigned long to eliminate that
> possibilities. This does not break UAPI.
> 
> Fixes: b507808ebce2 ("mm: implement memory-deny-write-execute as a prctl")
> Cc: linux-stable@...r.kernel.org
> Signed-off-by: Florent Revest <revest@...omium.org>

Ah yes. I remember this pain with seccomp. :)

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook