linux-kernel - Re: [PATCH] lkdtm: print real addresses

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Date:   Tue, 27 Nov 2018 08:43:27 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Christophe Leroy <christophe.leroy@....fr>
Cc:     Kees Cook <keescook@...omium.org>, Arnd Bergmann <arnd@...db.de>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] lkdtm: print real addresses

On Wed, Nov 07, 2018 at 08:14:10PM +0000, Christophe Leroy wrote:
> Today, when doing a lkdtm test before the readiness of the
> random generator, (ptrval) is printed instead of the address
> at which it perform the fault:
> 
> [ 1597.337030] lkdtm: Performing direct entry EXEC_USERSPACE
> [ 1597.337142] lkdtm: attempting ok execution at (ptrval)
> [ 1597.337398] lkdtm: attempting bad execution at (ptrval)
> [ 1597.337460] kernel tried to execute user page (77858000) -exploit attempt? (uid: 0)
> [ 1597.344769] Unable to handle kernel paging request for instruction fetch
> [ 1597.351392] Faulting instruction address: 0x77858000
> [ 1597.356312] Oops: Kernel access of bad area, sig: 11 [#1]
> 
> If the lkdtm test is done later on, it prints an hashed address.
> 
> In both cases this is pointless. The purpose of the test is to
> ensure the kernel generates an Oops at the expected address,
> so real addresses needs to be printed. This patch fixes that.

I am pretty sure this is intentional.  Kees?