linux-kernel - Re: [PATCH] x86/mm: Disable W^X detection and enforcement on 32-bit

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Message-ID: <202209232126.64AA2AC570@keescook>
Date:   Fri, 23 Sep 2022 21:26:36 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Dave Hansen <dave.hansen@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, Guenter Roeck <linux@...ck-us.net>,
        Ard Biesheuvel <ardb@...nel.org>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, linux-efi@...r.kernel.org,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] x86/mm: Disable W^X detection and enforcement on 32-bit

On Fri, Sep 23, 2022 at 03:17:30PM -0700, Dave Hansen wrote:
> The 32-bit code is in a weird spot.  Some 32-bit builds (non-PAE) do not
> even have NX support.  Even PAE builds that support NX have to contend
> with things like EFI data and code mixed in the same pages where W+X
> is unavoidable.
> 
> The folks still running X86_32=y kernels are unlikely to care much about
> NX.  That combined with the fundamental inability fix _all_ of the W+X
> things means this code had little value on X86_32=y.  Disable the checks.
> 
> Reported-by: Guenter Roeck <linux@...ck-us.net>
> Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>

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

-- 
Kees Cook