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[2620:137:e000::1:20]) by mx.google.com with ESMTP id r21-20020a632b15000000b0051b32aa267asi15552790pgr.671.2023.06.16.12.18.52; Fri, 16 Jun 2023 12:19:07 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@linutronix.de header.s=2020 header.b="WCBkg/lJ"; dkim=neutral (no key) header.i=@linutronix.de header.s=2020e header.b=ubK9ashO; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=linutronix.de Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345982AbjFPTSJ (ORCPT + 99 others); Fri, 16 Jun 2023 15:18:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48104 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345946AbjFPTRE (ORCPT ); Fri, 16 Jun 2023 15:17:04 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E565B3A8C; Fri, 16 Jun 2023 12:17:00 -0700 (PDT) Date: Fri, 16 Jun 2023 19:16:59 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1686943019; h=from:from:sender:sender:reply-to: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:content-transfer-encoding; bh=BvvSu6H6vVkBrXu/FX3I6M4fc3mykQ1OXzeO6E4gxJo=; b=WCBkg/lJ9xkeT7Scmdu3H7R9YBY6lyuMU3kj0UsLnxWjq3ewq63fIMAbkBfK4lI7jdTVzd 01hmhvuF89/VQ6754E0A2VH2RYHOPfRGNK1svF43c3E9jpRTHAmsE1aT0p5zxW8pjbJjxr 1Y1PFug5Zye5j7kTmVMv77BMtJiixviu23c6MEYr14BxdCgwH7CuHjHDhTv2NdVuIIjXi4 TEfCi3rNakJsnjGDBI8Z/EK7c7LQLnDGV/vMfPkEWvKQeVDTwashkRyr8ImPSCSwJ7CJ6W VY7itt79N8BP6jhDErRLDBd9KB1/b3CEUR2GRmbK8G3O3UIJ+g/gK/stXkmNyw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1686943019; h=from:from:sender:sender:reply-to: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:content-transfer-encoding; bh=BvvSu6H6vVkBrXu/FX3I6M4fc3mykQ1OXzeO6E4gxJo=; b=ubK9ashOOCmjzQxG4KaQENhDQOMd+hJ2RNg0vZDiVYmQ+sjdwYPOgNSfyOaCg22NxaHVuY CyL7A3SJqGPGiNAQ== From: "tip-bot2 for Rick Edgecombe" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/shstk] mm: Don't allow write GUPs to shadow stack memory Cc: Rick Edgecombe , Dave Hansen , "Borislav Petkov (AMD)" , Kees Cook , "Mike Rapoport (IBM)" , David Hildenbrand , Pengfei Xu , John Allen , x86@kernel.org, linux-kernel@vger.kernel.org MIME-Version: 1.0 Message-ID: <168694301906.404.6002060653010887598.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,SPF_HELO_NONE, SPF_PASS,T_SCC_BODY_TEXT_LINE,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1768888097347384884?= X-GMAIL-MSGID: =?utf-8?q?1768888097347384884?= The following commit has been merged into the x86/shstk branch of tip: Commit-ID: 620050abea57490acf2a2fc0d8b90d46c7a7edb9 Gitweb: https://git.kernel.org/tip/620050abea57490acf2a2fc0d8b90d46c7a7edb9 Author: Rick Edgecombe AuthorDate: Mon, 12 Jun 2023 17:10:48 -07:00 Committer: Dave Hansen CommitterDate: Thu, 15 Jun 2023 16:31:33 -07:00 mm: Don't allow write GUPs to shadow stack memory The x86 Control-flow Enforcement Technology (CET) feature includes a new type of memory called shadow stack. This shadow stack memory has some unusual properties, which requires some core mm changes to function properly. In userspace, shadow stack memory is writable only in very specific, controlled ways. However, since userspace can, even in the limited ways, modify shadow stack contents, the kernel treats it as writable memory. As a result, without additional work there would remain many ways for userspace to trigger the kernel to write arbitrary data to shadow stacks via get_user_pages(, FOLL_WRITE) based operations. To help userspace protect their shadow stacks, make this a little less exposed by blocking writable get_user_pages() operations for shadow stack VMAs. Still allow FOLL_FORCE to write through shadow stack protections, as it does for read-only protections. This is required for debugging use cases. Signed-off-by: Rick Edgecombe Signed-off-by: Dave Hansen Reviewed-by: Borislav Petkov (AMD) Reviewed-by: Kees Cook Acked-by: Mike Rapoport (IBM) Acked-by: David Hildenbrand Tested-by: Pengfei Xu Tested-by: John Allen Tested-by: Kees Cook Link: https://lore.kernel.org/all/20230613001108.3040476-23-rick.p.edgecombe%40intel.com --- arch/x86/include/asm/pgtable.h | 5 +++++ mm/gup.c | 2 +- 2 files changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index e846f0c..717d634 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -1630,6 +1630,11 @@ static inline bool __pte_access_permitted(unsigned long pteval, bool write) { unsigned long need_pte_bits = _PAGE_PRESENT|_PAGE_USER; + /* + * Write=0,Dirty=1 PTEs are shadow stack, which the kernel + * shouldn't generally allow access to, but since they + * are already Write=0, the below logic covers both cases. + */ if (write) need_pte_bits |= _PAGE_RW; diff --git a/mm/gup.c b/mm/gup.c index bbe4162..cc0dd52 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -978,7 +978,7 @@ static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags) return -EFAULT; if (write) { - if (!(vm_flags & VM_WRITE)) { + if (!(vm_flags & VM_WRITE) || (vm_flags & VM_SHADOW_STACK)) { if (!(gup_flags & FOLL_FORCE)) return -EFAULT; /* hugetlb does not support FOLL_FORCE|FOLL_WRITE. */