Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754148AbbLOSlO (ORCPT ); Tue, 15 Dec 2015 13:41:14 -0500 Received: from mail-oi0-f53.google.com ([209.85.218.53]:35966 "EHLO mail-oi0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753682AbbLOSlN (ORCPT ); Tue, 15 Dec 2015 13:41:13 -0500 MIME-Version: 1.0 In-Reply-To: References: <20151115070022.GA15417@amd> <20151214080403.GA3708@amd> <20151214085803.GA10520@pd.tnic> <20151214090726.GA6472@amd> <20151214202627.GA15104@amd> <566F3378.8070009@linux.intel.com> <20151215094015.GA3677@amd> From: Andy Lutomirski Date: Tue, 15 Dec 2015 10:40:53 -0800 Message-ID: Subject: Re: 4.4-rc5: ugly warn on: 5 W+X pages found To: Linus Torvalds Cc: Pavel Machek , Arjan van de Ven , Borislav Petkov , kernel list , Stephen Smalley , Brian Gerst , Denys Vlasenko , Peter Anvin , Mike Galbraith , Peter Zijlstra , Thomas Gleixner Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2311 Lines: 60 On Tue, Dec 15, 2015 at 9:45 AM, Linus Torvalds wrote: > On Tue, Dec 15, 2015 at 1:40 AM, Pavel Machek 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) && > + (protval & _PAGE_RW); > +} > + > /* > * Mask out unsupported bits in a present pgprot. Non-present pgprots > * can use those bits for other purposes, so leave them be. > @@ -345,8 +352,10 @@ static inline pgprotval_t massage_pgprot(pgprot_t pgprot) > { > pgprotval_t protval = pgprot_val(pgprot); > > - if (protval & _PAGE_PRESENT) > + if (protval & _PAGE_PRESENT) { > protval &= __supported_pte_mask; > + WARN_ON_ONCE(kernel_write_execute_prot(protval)); Shouldn't we switch those two lines? Arguably trying to set rwx permissions on !PAE is a bug even if it makes no difference, whereas setting rw- and getting rwx because we don't have NX support on the platform or kernel build doesn't indicate a bug. Anyway, I still think that we should apply my patches for 4.5 because I think they're cleanups, but apparently I guessed wrong as to what was causing Pavel's issue. But your patch would help diagnose it. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/