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 83049C7EE2D for ; Mon, 8 May 2023 10:28:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234592AbjEHK2e (ORCPT ); Mon, 8 May 2023 06:28:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54812 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234600AbjEHK2F (ORCPT ); Mon, 8 May 2023 06:28:05 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7CBC410EA for ; Mon, 8 May 2023 03:27:49 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id EE63E6263B for ; Mon, 8 May 2023 10:27:48 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DC503C433D2; Mon, 8 May 2023 10:27:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1683541668; bh=deALM/LeI2/1e0uypqYqUuOeZENR5t6MAL43V+qFw0Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Xfn0jOJ+QXN6fns/RAhDVStJtYri/QnZTJlE5A9t0swGU9R2XX2Y2zzlbtdQ3tuw6 ZLus6gNnSdFZ3iye0dtD8BkCz09nTXv08Oi2SsbX52ZWrWIx0qU3A+7jij2JBHOwCP 6emwwWSHBIC2HRzuBRmjX9mylr0tq/QRlflYKg+s= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Dionna Glaze , "Borislav Petkov (AMD)" , Sasha Levin Subject: [PATCH 6.2 188/663] virt/coco/sev-guest: Double-buffer messages Date: Mon, 8 May 2023 11:40:14 +0200 Message-Id: <20230508094434.520435294@linuxfoundation.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20230508094428.384831245@linuxfoundation.org> References: <20230508094428.384831245@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Dionna Glaze [ Upstream commit 965006103a14703cc42043bbf9b5e0cdf7a468ad ] 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 Signed-off-by: Sasha Levin --- 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 46f1a8d558b0b..0c7b47acba2a8 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)); @@ -417,13 +428,21 @@ 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) { if (rc == -EIO && *fw_err == SNP_GUEST_REQ_INVALID_LEN) -- 2.39.2