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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0FAAAC4332F for ; Tue, 15 Nov 2022 20:23:44 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 69D316B0071; Tue, 15 Nov 2022 15:23:44 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 64D506B0072; Tue, 15 Nov 2022 15:23:44 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 515358E0001; Tue, 15 Nov 2022 15:23:44 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 42DAA6B0071 for ; Tue, 15 Nov 2022 15:23:44 -0500 (EST) Received: from smtpin14.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 1AA011A051F for ; Tue, 15 Nov 2022 20:23:44 +0000 (UTC) X-FDA: 80136802368.14.3594168 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf25.hostedemail.com (Postfix) with ESMTP id 17CFCA0004 for ; Tue, 15 Nov 2022 20:23:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=gnBvvxVV1UpbhnAgdQuR60qQfn+qU/4SZdVegL+aLWo=; b=LmvA3vAEQOk+haDdY2beDBXSSP 6AG+A8DZNza9ah+lsNly31dFG5mbH+KdLxVxoe4weSk/onjV1PKnsjqogmTxI0TRkOKwjt76PGfxV ryCjwhnCnpxQlWcGw2b8eyoV1LtIALTk0hq2rQtes8YCxLJiEevIb1Td4E/s6uVQdst10xieyUcVC LxdQDXqrZU+SR3MZzD902ZPjTWxiAu4GVjChPwBUa50X5FYPJ48nFs9jml3cvb8+1FVVDq2wE5mu4 dFbUysFVCabBsNmJSpgZalRI4wvO1WrC5+0o3RuMr0DqvxiyzLoNKZn0liARiO28ZulfzwnlPOZSl 4Y175GZA==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1ov2T0-00GbpX-VG; Tue, 15 Nov 2022 20:23:35 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id A64BA300E7E; Tue, 15 Nov 2022 13:05:50 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 953572015BE8A; Tue, 15 Nov 2022 13:05:50 +0100 (CET) Date: Tue, 15 Nov 2022 13:05:50 +0100 From: Peter Zijlstra To: Rick Edgecombe Cc: x86@kernel.org, "H . Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H . J . Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Randy Dunlap , "Ravi V . Shankar" , Weijiang Yang , "Kirill A . Shutemov" , John Allen , kcc@google.com, eranian@google.com, rppt@kernel.org, jamorris@linux.microsoft.com, dethoma@microsoft.com, akpm@linux-foundation.org, Yu-cheng Yu Subject: Re: [PATCH v3 20/37] mm/mprotect: Exclude shadow stack from preserve_write Message-ID: References: <20221104223604.29615-1-rick.p.edgecombe@intel.com> <20221104223604.29615-21-rick.p.edgecombe@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221104223604.29615-21-rick.p.edgecombe@intel.com> ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1668543823; a=rsa-sha256; cv=none; b=VQ0zmoZCTLYifA5iRg4EhKQl0i4EqJQHLbGVcskf111U/ZOM73UvtYJd+QAt5pqLcEkiFb mS25p5B3U8IGlMp8gUY/xGtGkH3AqOBd5AvY/Rld77ba0Ye4zV1hAudYI+nLMHF5T3APvC 9MNqJYdxeqhCa8T1iQYGvz8+hg63FGc= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=LmvA3vAE; dmarc=none; spf=none (imf25.hostedemail.com: domain of peterz@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=peterz@infradead.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1668543823; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=gnBvvxVV1UpbhnAgdQuR60qQfn+qU/4SZdVegL+aLWo=; b=18lWscQwnCH7dcvSmNd7HEzmRiutvUqVpRN8MRKEJyAnA60MPveVO6Ua1nAUaQlDsGAN+q mv7u0sq4BJBOIK5wXtpe/aMV6bHAAnxA0vFnn73SBC2h3L2XihtZ9pJ7GvrUw+tyav8dLw 44/RrW7ooPjP88RfKchQJw6SZrclNpU= X-Rspamd-Queue-Id: 17CFCA0004 X-Rspam-User: Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=LmvA3vAE; dmarc=none; spf=none (imf25.hostedemail.com: domain of peterz@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=peterz@infradead.org X-Rspamd-Server: rspam06 X-Stat-Signature: ca9um95pdxkzso8ai5y1stenbmi1dgfb X-HE-Tag: 1668543822-62816 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Nov 04, 2022 at 03:35:47PM -0700, Rick Edgecombe wrote: > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 73b9b78f8cf4..7643a4db1b50 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -1803,6 +1803,13 @@ int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, > return 0; > > preserve_write = prot_numa && pmd_write(*pmd); > + > + /* > + * Preserve only normal writable huge PMD, but not shadow > + * stack (RW=0, Dirty=1). > + */ > + if (vma->vm_flags & VM_SHADOW_STACK) > + preserve_write = false; > ret = 1; > > #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION > diff --git a/mm/mprotect.c b/mm/mprotect.c > index 668bfaa6ed2a..ea82ce5f38fe 100644 > --- a/mm/mprotect.c > +++ b/mm/mprotect.c > @@ -115,6 +115,13 @@ static unsigned long change_pte_range(struct mmu_gather *tlb, > pte_t ptent; > bool preserve_write = prot_numa && pte_write(oldpte); > > + /* > + * Preserve only normal writable PTE, but not shadow > + * stack (RW=0, Dirty=1). > + */ > + if (vma->vm_flags & VM_SHADOW_STACK) > + preserve_write = false; > + > /* > * Avoid trapping faults against the zero or KSM > * pages. See similar comment in change_huge_pmd. These comments lack a why component; someone is going to wonder wtf this code is doing in the near future -- that someone might be you.