From patchwork Sat May 13 22:04:15 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Kirill A. Shutemov" X-Patchwork-Id: 681643 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 E5C53C77B7D for ; Sat, 13 May 2023 22:05:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230430AbjEMWE6 (ORCPT ); Sat, 13 May 2023 18:04:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57462 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231916AbjEMWEy (ORCPT ); Sat, 13 May 2023 18:04:54 -0400 Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 281AD30D3; Sat, 13 May 2023 15:04:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1684015493; x=1715551493; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=gRzQhhRAaTLGAt93TT2mPFzt+Xa/PSDkJomh6JXhxmM=; b=JKCPO3y8WHafsRVcc8rBjjeYO2gMypANbGvtZJTuZZpNNjkZH/8CFTpP XU3D16vOMyMyuqY+bxbVKzZHSrV+fWwg41TDTlKdGhbKnWCNg5PXro0YW 12Q8Uxe8AkVhps14Xi4qt/TAy6IdsCOQlbkEUtEKyuAVMV3nRJi3pYAdu UOvtYlGby0TFWW1RRi142GR0T/Hm1kpxkdYaYtOB+7p0rbxpikXe0NPjS dZJOPoJOSnVttkBrKv5/hbCL4lHuYb9e7pZYOcNiI3t8jCyb7hC+cbmK8 a3eT6fnYUvIE6SSen2eJD95stN5sr22jh3jpd7GcPD6SjcxdxMUv4xByu A==; X-IronPort-AV: E=McAfee;i="6600,9927,10709"; a="437325202" X-IronPort-AV: E=Sophos;i="5.99,273,1677571200"; d="scan'208";a="437325202" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 May 2023 15:04:52 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10709"; a="790199674" X-IronPort-AV: E=Sophos;i="5.99,273,1677571200"; d="scan'208";a="790199674" Received: from sorinaau-mobl1.ger.corp.intel.com (HELO box.shutemov.name) ([10.252.62.145]) by fmsmga003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 May 2023 15:04:45 -0700 Received: by box.shutemov.name (Postfix, from userid 1000) id 1A75810CF7C; Sun, 14 May 2023 01:04:34 +0300 (+03) From: "Kirill A. Shutemov" To: Borislav Petkov , Andy Lutomirski , Dave Hansen , Sean Christopherson , Andrew Morton , Joerg Roedel , Ard Biesheuvel Cc: Andi Kleen , Kuppuswamy Sathyanarayanan , David Rientjes , Vlastimil Babka , Tom Lendacky , Thomas Gleixner , Peter Zijlstra , Paolo Bonzini , Ingo Molnar , Dario Faggioli , Mike Rapoport , David Hildenbrand , Mel Gorman , marcelo.cerri@canonical.com, tim.gardner@canonical.com, khalid.elmously@canonical.com, philip.cox@canonical.com, aarcange@redhat.com, peterx@redhat.com, x86@kernel.org, linux-mm@kvack.org, linux-coco@lists.linux.dev, linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" , Dave Hansen Subject: [PATCHv11 6/9] efi/unaccepted: Avoid load_unaligned_zeropad() stepping into unaccepted memory Date: Sun, 14 May 2023 01:04:15 +0300 Message-Id: <20230513220418.19357-7-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 2.39.3 In-Reply-To: <20230513220418.19357-1-kirill.shutemov@linux.intel.com> References: <20230513220418.19357-1-kirill.shutemov@linux.intel.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org load_unaligned_zeropad() can lead to unwanted loads across page boundaries. The unwanted loads are typically harmless. But, they might be made to totally unrelated or even unmapped memory. load_unaligned_zeropad() relies on exception fixup (#PF, #GP and now #VE) to recover from these unwanted loads. But, this approach does not work for unaccepted memory. For TDX, a load from unaccepted memory will not lead to a recoverable exception within the guest. The guest will exit to the VMM where the only recourse is to terminate the guest. There are two parts to fix this issue and comprehensively avoid access to unaccepted memory. Together these ensure that an extra "guard" page is accepted in addition to the memory that needs to be used. 1. Implicitly extend the range_contains_unaccepted_memory(start, end) checks up to end+unit_size if 'end' is aligned on a unit_size boundary. 2. Implicitly extend accept_memory(start, end) to end+unit_size if 'end' is aligned on a unit_size boundary. Side note: This leads to something strange. Pages which were accepted at boot, marked by the firmware as accepted and will never _need_ to be accepted might be on unaccepted_pages list This is a cue to ensure that the next page is accepted before 'page' can be used. This is an actual, real-world problem which was discovered during TDX testing. Signed-off-by: Kirill A. Shutemov Reviewed-by: Dave Hansen Reviewed-by: Ard Biesheuvel Reviewed-by: Tom Lendacky --- drivers/firmware/efi/unaccepted_memory.c | 35 ++++++++++++++++++++++++ 1 file changed, 35 insertions(+) diff --git a/drivers/firmware/efi/unaccepted_memory.c b/drivers/firmware/efi/unaccepted_memory.c index bb91c41f76fb..3d1ca60916dd 100644 --- a/drivers/firmware/efi/unaccepted_memory.c +++ b/drivers/firmware/efi/unaccepted_memory.c @@ -37,6 +37,34 @@ void accept_memory(phys_addr_t start, phys_addr_t end) start -= unaccepted->phys_base; end -= unaccepted->phys_base; + /* + * load_unaligned_zeropad() can lead to unwanted loads across page + * boundaries. The unwanted loads are typically harmless. But, they + * might be made to totally unrelated or even unmapped memory. + * load_unaligned_zeropad() relies on exception fixup (#PF, #GP and now + * #VE) to recover from these unwanted loads. + * + * But, this approach does not work for unaccepted memory. For TDX, a + * load from unaccepted memory will not lead to a recoverable exception + * within the guest. The guest will exit to the VMM where the only + * recourse is to terminate the guest. + * + * There are two parts to fix this issue and comprehensively avoid + * access to unaccepted memory. Together these ensure that an extra + * "guard" page is accepted in addition to the memory that needs to be + * used: + * + * 1. Implicitly extend the range_contains_unaccepted_memory(start, end) + * checks up to end+unit_size if 'end' is aligned on a unit_size + * boundary. + * + * 2. Implicitly extend accept_memory(start, end) to end+unit_size if + * 'end' is aligned on a unit_size boundary. (immediately following + * this comment) + */ + if (!(end % unit_size)) + end += unit_size; + /* Make sure not to overrun the bitmap */ if (end > unaccepted->size * unit_size * BITS_PER_BYTE) end = unaccepted->size * unit_size * BITS_PER_BYTE; @@ -84,6 +112,13 @@ bool range_contains_unaccepted_memory(phys_addr_t start, phys_addr_t end) start -= unaccepted->phys_base; end -= unaccepted->phys_base; + /* + * Also consider the unaccepted state of the *next* page. See fix #1 in + * the comment on load_unaligned_zeropad() in accept_memory(). + */ + if (!(end % unit_size)) + end += unit_size; + /* Make sure not to overrun the bitmap */ if (end > unaccepted->size * unit_size * BITS_PER_BYTE) end = unaccepted->size * unit_size * BITS_PER_BYTE;