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 6ACC6C61DA4 for ; Thu, 16 Feb 2023 12:46:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230301AbjBPMqT (ORCPT ); Thu, 16 Feb 2023 07:46:19 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56342 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229946AbjBPMqL (ORCPT ); Thu, 16 Feb 2023 07:46:11 -0500 Received: from mail.skyhub.de (mail.skyhub.de [5.9.137.197]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 060172D67 for ; Thu, 16 Feb 2023 04:46:06 -0800 (PST) Received: from zn.tnic (p5de8e9fe.dip0.t-ipconnect.de [93.232.233.254]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id A22871EC0936; Thu, 16 Feb 2023 13:46:04 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1676551564; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=W4fNzZVp6ePbAT+6Jjwj3b2oeBPQ7cQ0clPlhPYCkY4=; b=W5gYmg9/rgBZ+OYxwfvMa476vZXL8ADyRXj63MQ0zCaQijXtG+7EODhCVi6QBrHgl2OSH2 rlhEvCBj4RLcXFxZS19tHln3awVB6OJNxIo3TyLgTA1vmWymZ+6nsLxb7snaarMddYJCKA rkyi2tXWDyw7ZG2OeMzshhZZ34dIcRs= From: Borislav Petkov To: LKML Cc: Dionna Glaze , Joerg Roedel , Michael Roth , Nikunj A Dadhania , Peter Gonda , Tom Lendacky , linux-coco@lists.linux.dev, x86@kernel.org Subject: [PATCH 09/11] virt/coco/sev-guest: Double-buffer messages Date: Thu, 16 Feb 2023 13:46:00 +0100 Message-Id: <20230216124602.26849-4-bp@alien8.de> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20230216124602.26849-1-bp@alien8.de> References: <20230216124120.26578-1-bp@alien8.de> <20230216124602.26849-1-bp@alien8.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Dionna Glaze The encryption algorithms read and write directly to shared unencrypted memory, which may leak information as well as permit the host to tamper with the message integrity. Instead, copy whole messages in or out as needed before doing any computation on them. Fixes: d5af44dde546 ("x86/sev: Provide support for SNP guest request NAEs") Signed-off-by: Dionna Glaze Signed-off-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/r/20230214164638.1189804-3-dionnaglaze@google.com --- drivers/virt/coco/sev-guest/sev-guest.c | 27 +++++++++++++++++++++---- 1 file changed, 23 insertions(+), 4 deletions(-) diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c index ca501d119233..070c6f414bfd 100644 --- a/drivers/virt/coco/sev-guest/sev-guest.c +++ b/drivers/virt/coco/sev-guest/sev-guest.c @@ -46,7 +46,15 @@ struct snp_guest_dev { void *certs_data; struct snp_guest_crypto *crypto; + /* request and response are in unencrypted memory */ struct snp_guest_msg *request, *response; + + /* + * Avoid information leakage by double-buffering shared messages + * in fields that are in regular encrypted memory. + */ + struct snp_guest_msg secret_request, secret_response; + struct snp_secrets_page_layout *layout; struct snp_req_data input; u32 *os_area_msg_seqno; @@ -266,14 +274,17 @@ static int dec_payload(struct snp_guest_dev *snp_dev, struct snp_guest_msg *msg, static int verify_and_dec_payload(struct snp_guest_dev *snp_dev, void *payload, u32 sz) { struct snp_guest_crypto *crypto = snp_dev->crypto; - struct snp_guest_msg *resp = snp_dev->response; - struct snp_guest_msg *req = snp_dev->request; + struct snp_guest_msg *resp = &snp_dev->secret_response; + struct snp_guest_msg *req = &snp_dev->secret_request; struct snp_guest_msg_hdr *req_hdr = &req->hdr; struct snp_guest_msg_hdr *resp_hdr = &resp->hdr; dev_dbg(snp_dev->dev, "response [seqno %lld type %d version %d sz %d]\n", resp_hdr->msg_seqno, resp_hdr->msg_type, resp_hdr->msg_version, resp_hdr->msg_sz); + /* Copy response from shared memory to encrypted memory. */ + memcpy(resp, snp_dev->response, sizeof(*resp)); + /* Verify that the sequence counter is incremented by 1 */ if (unlikely(resp_hdr->msg_seqno != (req_hdr->msg_seqno + 1))) return -EBADMSG; @@ -297,7 +308,7 @@ static int verify_and_dec_payload(struct snp_guest_dev *snp_dev, void *payload, static int enc_payload(struct snp_guest_dev *snp_dev, u64 seqno, int version, u8 type, void *payload, size_t sz) { - struct snp_guest_msg *req = snp_dev->request; + struct snp_guest_msg *req = &snp_dev->secret_request; struct snp_guest_msg_hdr *hdr = &req->hdr; memset(req, 0, sizeof(*req)); @@ -400,13 +411,21 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in if (!seqno) return -EIO; + /* Clear shared memory's response for the host to populate. */ memset(snp_dev->response, 0, sizeof(struct snp_guest_msg)); - /* Encrypt the userspace provided payload */ + /* Encrypt the userspace provided payload in snp_dev->secret_request. */ rc = enc_payload(snp_dev, seqno, msg_ver, type, req_buf, req_sz); if (rc) return rc; + /* + * Write the fully encrypted request to the shared unencrypted + * request page. + */ + memcpy(snp_dev->request, &snp_dev->secret_request, + sizeof(snp_dev->secret_request)); + rc = __handle_guest_request(snp_dev, exit_code, fw_err); if (rc) { dev_alert(snp_dev->dev, "Detected error from ASP request. rc: %d, fw_err: %llu\n", rc, *fw_err); -- 2.35.1