From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2D947ECAA27 for ; Thu, 25 Aug 2022 17:18:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240934AbiHYRSa (ORCPT ); Thu, 25 Aug 2022 13:18:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50236 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242134AbiHYRST (ORCPT ); Thu, 25 Aug 2022 13:18:19 -0400 Received: from mail-pf1-x431.google.com (mail-pf1-x431.google.com [IPv6:2607:f8b0:4864:20::431]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C3A48BC834 for ; Thu, 25 Aug 2022 10:18:18 -0700 (PDT) Received: by mail-pf1-x431.google.com with SMTP id 67so12233650pfv.2 for ; Thu, 25 Aug 2022 10:18:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc; bh=gnMljPJ/lm4q/RBQXlsRGj0qaMzhOLblX5QXKQT9GOA=; b=p1XusnwBuXPciTUrnlwiAdph5OC6EkXk+q666UtGjiflFY51AQZo97IAR+bXvBE5mc 6ZnwuE95uHUD9rAwsuB/gtyXhWQJwLI85ad5uXmJjUUNquSP3RzKzdeAlXyC99WVlm3R Y2lh8kQTg0EL/k5qB2L6VdySGhKh+I7I+ijgqd5xFk6Le4GhtS0Nk9THw5+VUlFpCYJI /HFiss9A50VlnXbP24JxGRhOojtOvQi3M31evuhjT92gnr7Fx1EAGVDT8Ys06xTC9MIS tZSV/bVEufRX/bA3tqR1mhypO9d7NYqoJHS6MHJy5HTfpGDzxuI3okYr/7DFGgHTxpRS t0Mg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc; bh=gnMljPJ/lm4q/RBQXlsRGj0qaMzhOLblX5QXKQT9GOA=; b=n13+/84WgxRZDoFS+adCYPalD1Adzaff+Dqa98fyk6o9owZk8c9Tuhp23yCPY8ie2E Db5RtglJzJFBtzlaA/iEqOTb37AOcVUnJjq76PinSJCUZDW2WufUrWsmDk+2hff9gp1E OrEzC2aHXtVl3Sh09hW1u26FLEv7v1ynuhs3jtDdpIgkvp0qLZixhqoSE439jTCQgMC2 G5oOCMiSwkt6Of90DW3ccRkYk/BED65VTl/bfGTwnLQ8dQEl9p9Fv2TavsREzxnBpM7g VE3pqzm35AP3M9DSBwpf/w1uyVXgr+isp3GCqFnC++Vew0wssMe7Bvqi3pJE2IoeQ3Uk 6UoQ== X-Gm-Message-State: ACgBeo1d/Gxj2xaE7kKyA89jvz58E1VdfHoxR7VZOVsbsBSSG0Aj8kty NiOAxY0CoxAueWj7IzPCQSvtiw== X-Google-Smtp-Source: AA6agR6tK/D5enD9fgdi0ecU+FGxTwOMoe8z3P512kBNwxfyORCYzrkGCt7PVHxGWuY2Ef4fCuM4Vw== X-Received: by 2002:a63:494a:0:b0:41c:f29e:2a2e with SMTP id y10-20020a63494a000000b0041cf29e2a2emr78650pgk.477.1661447898207; Thu, 25 Aug 2022 10:18:18 -0700 (PDT) Received: from google.com (7.104.168.34.bc.googleusercontent.com. [34.168.104.7]) by smtp.gmail.com with ESMTPSA id l63-20020a622542000000b00535e49245d6sm15216396pfl.12.2022.08.25.10.18.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 25 Aug 2022 10:18:17 -0700 (PDT) Date: Thu, 25 Aug 2022 17:18:13 +0000 From: Sean Christopherson To: Peter Zijlstra Cc: Dave Hansen , x86@kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, keescook@chromium.org Subject: Re: [PATCH] x86/mm: Refuse W^X violations Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 25, 2022, Peter Zijlstra wrote: > > x86 has STRICT_*_RWX, but not even a warning when someone violates it. > > Add this warning and fully refuse the transition. > > Signed-off-by: Peter Zijlstra (Intel) > --- > diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c > index 1abd5438f126..9e9bef3f36b3 100644 > --- a/arch/x86/mm/pat/set_memory.c > +++ b/arch/x86/mm/pat/set_memory.c > @@ -579,6 +579,30 @@ static inline pgprot_t static_protections(pgprot_t prot, unsigned long start, > return __pgprot(pgprot_val(prot) & ~forbidden); > } > > +/* > + * Validate and enforce strict W^X semantics. > + */ > +static inline pgprot_t verify_rwx(pgprot_t old, pgprot_t new, unsigned long start, > + unsigned long pfn, unsigned long npg) > +{ > + unsigned long end; > + I think this needs if (!(__supported_pte_mask & _PAGE_NX)) return new; to play nice with non-PAE 32-bit kernels. > + if (!((pgprot_val(old) ^ pgprot_val(new)) & (_PAGE_RW | _PAGE_NX))) > + return new; > + > + if ((pgprot_val(new) & (_PAGE_RW | _PAGE_NX)) != _PAGE_RW) > + return new; > + > + end = start + npg * PAGE_SIZE - 1; > + WARN(1, "CPA refuse W^X violation: %016llx -> %016llx range: 0x%016lx - 0x%016lx PFN %lx\n", WARN_ONCE() to avoid eternal spam if something does go sideways? > + (unsigned long long)pgprot_val(old), > + (unsigned long long)pgprot_val(new), > + start, end, pfn); > + > + /* refuse the transition into WX */ > + return old; > +}