From nobody Sun Feb 8 00:49:27 2026 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 E3A3EC001E0 for ; Tue, 1 Aug 2023 15:54:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235030AbjHAPyw (ORCPT ); Tue, 1 Aug 2023 11:54:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36680 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235022AbjHAPyq (ORCPT ); Tue, 1 Aug 2023 11:54:46 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5505E1AA for ; Tue, 1 Aug 2023 08:53:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1690905237; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=6ii4XAGrPtq5rfz/6VphDSYMVOAoJKA+/p4wdrDYiew=; b=N64ny0aE/gswuWppgE2Q3IiACIZdC25TaKqpAVp01xK4UwTkNTu4KiPYS3MgoamPuL1VBO 78b6KtBUkAL0+vc/rjLJQIVb2Ji7mUjvjymXiccqO0qC28BQM8mcCW12vsVCTTTy5EK5EZ Oh2f+7Gbz+mg0s3dsXeUo6Vdgiaoj64= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-145-6uWu9M3XOamg6JMuPLV17g-1; Tue, 01 Aug 2023 11:53:55 -0400 X-MC-Unique: 6uWu9M3XOamg6JMuPLV17g-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 4E3A0185A78F; Tue, 1 Aug 2023 15:53:55 +0000 (UTC) Received: from localhost (unknown [10.39.195.12]) by smtp.corp.redhat.com (Postfix) with ESMTP id ACDE61454148; Tue, 1 Aug 2023 15:53:54 +0000 (UTC) From: Stefan Hajnoczi To: Alex Williamson Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Stefan Hajnoczi Subject: [PATCH] vfio/type1: fix cap_migration information leak Date: Tue, 1 Aug 2023 11:53:52 -0400 Message-ID: <20230801155352.1391945-1-stefanha@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Fix an information leak where an uninitialized hole in struct vfio_iommu_type1_info_cap_migration on the stack is exposed to userspace. The definition of struct vfio_iommu_type1_info_cap_migration contains a hol= e as shown in this pahole(1) output: struct vfio_iommu_type1_info_cap_migration { struct vfio_info_cap_header header; /* 0 8 */ __u32 flags; /* 8 4 */ /* XXX 4 bytes hole, try to pack */ __u64 pgsize_bitmap; /* 16 8 */ __u64 max_dirty_bitmap_size; /* 24 8 = */ /* size: 32, cachelines: 1, members: 4 */ /* sum members: 28, holes: 1, sum holes: 4 */ /* last cacheline: 32 bytes */ }; The cap_mig variable is filled in without initializing the hole: static int vfio_iommu_migration_build_caps(struct vfio_iommu *iommu, struct vfio_info_cap *caps) { struct vfio_iommu_type1_info_cap_migration cap_mig; cap_mig.header.id =3D VFIO_IOMMU_TYPE1_INFO_CAP_MIGRATION; cap_mig.header.version =3D 1; cap_mig.flags =3D 0; /* support minimum pgsize */ cap_mig.pgsize_bitmap =3D (size_t)1 << __ffs(iommu->pgsize_bitmap); cap_mig.max_dirty_bitmap_size =3D DIRTY_BITMAP_SIZE_MAX; return vfio_info_add_capability(caps, &cap_mig.header, sizeof(cap_mig= )); } The structure is then copied to a temporary location on the heap. At this p= oint it's already too late and ioctl(VFIO_IOMMU_GET_INFO) copies it to userspace later: int vfio_info_add_capability(struct vfio_info_cap *caps, struct vfio_info_cap_header *cap, size_t size) { struct vfio_info_cap_header *header; header =3D vfio_info_cap_add(caps, size, cap->id, cap->version); if (IS_ERR(header)) return PTR_ERR(header); memcpy(header + 1, cap + 1, size - sizeof(*header)); return 0; } This issue was found by code inspection. Signed-off-by: Stefan Hajnoczi Reviewed-by: Kevin Tian --- drivers/vfio/vfio_iommu_type1.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type= 1.c index ebe0ad31d0b0..d662aa9d1b4b 100644 --- a/drivers/vfio/vfio_iommu_type1.c +++ b/drivers/vfio/vfio_iommu_type1.c @@ -2732,7 +2732,7 @@ static int vfio_iommu_iova_build_caps(struct vfio_iom= mu *iommu, static int vfio_iommu_migration_build_caps(struct vfio_iommu *iommu, struct vfio_info_cap *caps) { - struct vfio_iommu_type1_info_cap_migration cap_mig; + struct vfio_iommu_type1_info_cap_migration cap_mig =3D {}; =20 cap_mig.header.id =3D VFIO_IOMMU_TYPE1_INFO_CAP_MIGRATION; cap_mig.header.version =3D 1; --=20 2.41.0