Date: Tue, 15 Dec 2015 19:30:05 +0100
From: Borislav Petkov <bp@alien8.de>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Pavel Machek <pavel@ucw.cz>, Andy Lutomirski <luto@amacapital.net>,
        Arjan van de Ven <arjan@linux.intel.com>,
        kernel list <linux-kernel@vger.kernel.org>,
        Stephen Smalley <sds@tycho.nsa.gov>, Brian Gerst <brgerst@gmail.com>,
        Denys Vlasenko <dvlasenk@redhat.com>, Peter Anvin <hpa@zytor.com>,
        Mike Galbraith <efault@gmx.de>, Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: Re: 4.4-rc5: ugly warn on: 5 W+X pages found
Message-ID: <20151215183004.GI25973@pd.tnic>
References: <20151214080403.GA3708@amd>
 <20151214085803.GA10520@pd.tnic>
 <20151214090726.GA6472@amd>
 <CA+55aFwivS6pnNKqy6aFrh4H5HC2izW_Rw0GL1hV9EdbV+HhkA@mail.gmail.com>
 <20151214202627.GA15104@amd>
 <CALCETrX6DrW2AJz=WGjMW+nNTsq08+Cte0m=CF_Q9+uzsuR1vA@mail.gmail.com>
 <566F3378.8070009@linux.intel.com>
 <CALCETrW60DfZs-v_W46sYFUmBXspa3BXWY-=dpuSF9iMaeLGFQ@mail.gmail.com>
 <20151215094015.GA3677@amd>
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On Tue, Dec 15, 2015 at 09:45:40AM -0800, Linus Torvalds wrote:
> On Tue, Dec 15, 2015 at 1:40 AM, Pavel Machek <pavel@ucw.cz> wrote:
> >
> > I tried applying:
> >
> > [PATCH 1/2] x86_32/mm: Set NX in __supported_pte_mask before enabling
> > paging
> >
> > but I still get
> >
> > [    2.691897] x86/mm: Found insecure W+X mapping at address ffe69000/0xffe69000
> 
> This may be an insane suggestion, but how about we try to detect when
> that entry gets set, rather than after the fact.
> 
> Something really brute-force like
> 
>   diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
>   index 6ec0c8b2e9df..538c9bb239b9 100644
>   --- a/arch/x86/include/asm/pgtable.h
>   +++ b/arch/x86/include/asm/pgtable.h
>   @@ -337,6 +337,13 @@ static inline pmd_t pmd_clear_soft_dirty(pmd_t pmd)
> 
>    #endif /* CONFIG_HAVE_ARCH_SOFT_DIRTY */
> 
>   +static inline int kernel_write_execute_prot(pgprotval_t protval)
>   +{
>   +       return !(protval & _PAGE_USER) &&
>   +               !(protval & _PAGE_NX) &&

Shouldn't this be without a "!"? AFAIU, we want _PAGE_NX | _PAGE_RW?

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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