From patchwork Tue May 21 07:45:46 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Norbert Manthey X-Patchwork-Id: 10953085 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id D157314C0 for ; Tue, 21 May 2019 07:48:57 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id C06572892C for ; Tue, 21 May 2019 07:48:57 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id B47C328961; Tue, 21 May 2019 07:48:57 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00,DKIM_ADSP_ALL, DKIM_INVALID,DKIM_SIGNED,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 2ACF22892C for ; Tue, 21 May 2019 07:48:57 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1hSzUo-0007w1-T4; Tue, 21 May 2019 07:47:38 +0000 Received: from us1-rack-dfw2.inumbo.com ([104.130.134.6]) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1hSzUn-0007vq-Hs for xen-devel@lists.xenproject.org; Tue, 21 May 2019 07:47:37 +0000 X-Inumbo-ID: b2ee79e8-7b9c-11e9-8980-bc764e045a96 Received: from smtp-fw-2101.amazon.com (unknown [72.21.196.25]) by us1-rack-dfw2.inumbo.com (Halon) with ESMTPS id b2ee79e8-7b9c-11e9-8980-bc764e045a96; Tue, 21 May 2019 07:47:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.de; i=@amazon.de; q=dns/txt; s=amazon201209; t=1558424856; x=1589960856; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version; bh=Gn4S26oLtLdOoPExfexD3mJ+nmKDf8huMc68XiI9qM4=; b=HUZBVcAXlKqdDrFA0nix+svQ6bnpLAE7WWhwlWdPWAz9KGNR6i56puls aG1arHghGZeXeAsKM7BXrBvnGVskNofzbDEHvYeLiONT5DcTGBK4D+tj4 0/nduD6YXg7iesx8fn2T/Kwm/H0OKySjSa4l5eASEBdirOkYIr/bHVCtQ Y=; X-IronPort-AV: E=Sophos;i="5.60,494,1549929600"; d="scan'208";a="733992446" Received: from iad6-co-svc-p1-lb1-vlan2.amazon.com (HELO email-inbound-relay-2a-1c1b5cdd.us-west-2.amazon.com) ([10.124.125.2]) by smtp-border-fw-out-2101.iad2.amazon.com with ESMTP/TLS/DHE-RSA-AES256-SHA; 21 May 2019 07:47:34 +0000 Received: from EX13MTAUEA001.ant.amazon.com (pdx1-ws-svc-p6-lb9-vlan3.pdx.amazon.com [10.236.137.198]) by email-inbound-relay-2a-1c1b5cdd.us-west-2.amazon.com (8.14.7/8.14.7) with ESMTP id x4L7lTff120976 (version=TLSv1/SSLv3 cipher=AES256-SHA bits=256 verify=FAIL); Tue, 21 May 2019 07:47:30 GMT Received: from EX13D08UEE001.ant.amazon.com (10.43.62.126) by EX13MTAUEA001.ant.amazon.com (10.43.61.82) with Microsoft SMTP Server (TLS) id 15.0.1367.3; Tue, 21 May 2019 07:47:19 +0000 Received: from EX13MTAUWB001.ant.amazon.com (10.43.161.207) by EX13D08UEE001.ant.amazon.com (10.43.62.126) with Microsoft SMTP Server (TLS) id 15.0.1367.3; Tue, 21 May 2019 07:47:19 +0000 Received: from uc1a35a69ae4659.ant.amazon.com (10.28.85.34) by mail-relay.amazon.com (10.43.161.249) with Microsoft SMTP Server id 15.0.1367.3 via Frontend Transport; Tue, 21 May 2019 07:47:15 +0000 From: Norbert Manthey To: Date: Tue, 21 May 2019 09:45:46 +0200 Message-ID: <1558424746-24059-4-git-send-email-nmanthey@amazon.de> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1558424746-24059-1-git-send-email-nmanthey@amazon.de> References: <1558424746-24059-1-git-send-email-nmanthey@amazon.de> MIME-Version: 1.0 Precedence: Bulk Subject: [Xen-devel] [PATCH L1TF MDS GT v1 3/3] common/grant_table: harden version dependent accesses X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Juergen Gross , Tim Deegan , Stefano Stabellini , Wei Liu , Konrad Rzeszutek Wilk , George Dunlap , Andrew Cooper , Ian Jackson , Dario Faggioli , Martin Pohlack , Pawel Wieczorkiewicz , Julien Grall , David Woodhouse , Jan Beulich , Martin Mazein , Bjoern Doebel , Norbert Manthey Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" X-Virus-Scanned: ClamAV using ClamSMTP Guests can issue grant table operations and provide guest controlled data to them. This data is used as index for memory loads after bound checks have been done. Depending on the grant table version, the size of elements in containers differ. As the base data structure is a page, the number of elements per page also differs. Consequently, bound checks are version dependent, so that speculative execution can happen in several stages, the bound check as well as the version check. This commit mitigates cases where out-of-bound accesses could happen due to the version comparison. In cases, where no different memory locations are accessed on the code path that follow an if statement, no protection is required. No different memory locations are accessed in the following functions after a version check: * gnttab_setup_table: only calculated numbersi are used, and then function gnttab_grow_table is called, which is version protected * gnttab_transfer: the case that depends on the version check just gets into copying a page or not * acquire_grant_for_copy: the not fixed comparison is on the abort path and does not access other structures, and on the else branch only accesses structures that are properly allocated * gnttab_set_version: all accessible data is allocated for both versions * gnttab_release_mappings: this function is called only during domain destruction and control is not returned to the guest * mem_sharing_gref_to_gfn: speculation will be stoped by the second if statement, as that places a barrier on any path to be executed. * gnttab_get_status_frame_mfn: no version dependent check, because all accesses, except the gt->status[idx], do not perform actual out-of-bound accesses, including the gnttab_grow_table function call. * gnttab_get_shared_frame: block_speculation in gnttab_get_status_frame_mfn blocks accesses * gnttab_usage_print: cannot be triggered by the guest This is part of the speculative hardening effort. Signed-off-by: Norbert Manthey --- Notes: v1: added additional fixes (compared to L1TF series) to: _set_status unmap_common_complete gnttab_grow_table xen/common/grant_table.c | 27 +++++++++++++++------------ 1 file changed, 15 insertions(+), 12 deletions(-) diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c --- a/xen/common/grant_table.c +++ b/xen/common/grant_table.c @@ -837,7 +837,7 @@ static int _set_status(unsigned gt_version, grant_status_t *status) { - if ( gt_version == 1 ) + if ( evaluate_nospec(gt_version == 1) ) return _set_status_v1(domid, readonly, mapflag, shah, act); else return _set_status_v2(domid, readonly, mapflag, shah, act, status); @@ -990,9 +990,12 @@ map_grant_ref( /* This call also ensures the above check cannot be passed speculatively */ shah = shared_entry_header(rgt, op->ref); - status = rgt->gt_version == 1 ? &shah->flags : &status_entry(rgt, op->ref); act = active_entry_acquire(rgt, op->ref); + /* Make sure we do not access memory speculatively */ + status = evaluate_nospec(rgt->gt_version == 1) ? &shah->flags + : &status_entry(rgt, op->ref); + /* If already pinned, check the active domid and avoid refcnt overflow. */ if ( act->pin && ((act->domid != ld->domain_id) || @@ -1013,7 +1016,7 @@ map_grant_ref( if ( !act->pin ) { - unsigned long gfn = rgt->gt_version == 1 ? + unsigned long gfn = evaluate_nospec(rgt->gt_version == 1) ? shared_entry_v1(rgt, op->ref).frame : shared_entry_v2(rgt, op->ref).full_page.frame; @@ -1463,7 +1466,7 @@ unmap_common_complete(struct gnttab_unmap_common *op) act = active_entry_acquire(rgt, op->ref); sha = shared_entry_header(rgt, op->ref); - if ( rgt->gt_version == 1 ) + if ( evaluate_nospec(rgt->gt_version == 1) ) status = &sha->flags; else status = &status_entry(rgt, op->ref); @@ -1795,7 +1798,7 @@ gnttab_grow_table(struct domain *d, unsigned int req_nr_frames) } /* Status pages - version 2 */ - if ( gt->gt_version > 1 ) + if ( evaluate_nospec(gt->gt_version > 1) ) { if ( gnttab_populate_status_frames(d, gt, req_nr_frames) ) goto shared_alloc_failed; @@ -2290,7 +2293,7 @@ gnttab_transfer( grant_read_lock(e->grant_table); act = active_entry_acquire(e->grant_table, gop.ref); - if ( e->grant_table->gt_version == 1 ) + if ( evaluate_nospec(e->grant_table->gt_version == 1) ) { grant_entry_v1_t *sha = &shared_entry_v1(e->grant_table, gop.ref); @@ -2351,7 +2354,7 @@ release_grant_for_copy( sha = shared_entry_header(rgt, gref); mfn = act->mfn; - if ( rgt->gt_version == 1 ) + if ( evaluate_nospec(rgt->gt_version == 1) ) { status = &sha->flags; td = rd; @@ -2449,7 +2452,7 @@ acquire_grant_for_copy( shah = shared_entry_header(rgt, gref); act = active_entry_acquire(rgt, gref); - if ( rgt->gt_version == 1 ) + if ( evaluate_nospec(rgt->gt_version == 1) ) { sha2 = NULL; status = &shah->flags; @@ -3269,7 +3272,7 @@ swap_grant_ref(grant_ref_t ref_a, grant_ref_t ref_b) if ( act_b->pin ) PIN_FAIL(out, GNTST_eagain, "ref b %#x busy\n", ref_b); - if ( gt->gt_version == 1 ) + if ( evaluate_nospec(gt->gt_version == 1) ) { grant_entry_v1_t shared; @@ -3818,7 +3821,7 @@ int mem_sharing_gref_to_gfn(struct grant_table *gt, grant_ref_t ref, rc = -EINVAL; else if ( ref >= nr_grant_entries(gt) ) rc = -ENOENT; - else if ( gt->gt_version == 1 ) + else if ( evaluate_nospec(gt->gt_version == 1) ) { const grant_entry_v1_t *sha1 = &shared_entry_v1(gt, ref); @@ -3840,7 +3843,7 @@ int mem_sharing_gref_to_gfn(struct grant_table *gt, grant_ref_t ref, rc = -ENXIO; else if ( !rc && status ) { - if ( gt->gt_version == 1 ) + if ( evaluate_nospec(gt->gt_version == 1) ) *status = flags; else *status = status_entry(gt, ref); @@ -3927,7 +3930,7 @@ int gnttab_map_frame(struct domain *d, unsigned long idx, gfn_t gfn, mfn_t *mfn) grant_write_lock(gt); - if ( gt->gt_version == 2 && (idx & XENMAPIDX_grant_table_status) ) + if ( evaluate_nospec(gt->gt_version == 2) && (idx & XENMAPIDX_grant_table_status) ) { idx &= ~XENMAPIDX_grant_table_status; status = true;