From patchwork Fri Apr 9 11:12:54 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ondrej Mosnacek X-Patchwork-Id: 12193763 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 82720C43603 for ; Fri, 9 Apr 2021 11:13:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5622E61105 for ; Fri, 9 Apr 2021 11:13:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233878AbhDILNX (ORCPT ); Fri, 9 Apr 2021 07:13:23 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:25567 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233852AbhDILNS (ORCPT ); Fri, 9 Apr 2021 07:13:18 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1617966785; 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: in-reply-to:in-reply-to:references:references; bh=m9DLwVwuEa/TUYn9CBVZYDMdn9III6hdDzVPKN/l5PE=; b=NI8oMmGDrIcvEO7isjFNL/S3787imHGYUd1LjP2nZ3wlSRXbigiHg/W35TgFr69PxraqT4 mOE65MKYL39mFVr2JY+mNyN3EBj+1QlRKVDGZIexRxCUBiftUzgniKJKdegJNSeD9OiIwW 7Ij5Dfrct/AK1jkCfY+B2AI11M5X+rE= Received: from mail-ej1-f72.google.com (mail-ej1-f72.google.com [209.85.218.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-336-Ki8LKVwSOY2_aZzLwgUKXg-1; Fri, 09 Apr 2021 07:13:02 -0400 X-MC-Unique: Ki8LKVwSOY2_aZzLwgUKXg-1 Received: by mail-ej1-f72.google.com with SMTP id gj5so1380495ejb.19 for ; Fri, 09 Apr 2021 04:13:02 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=m9DLwVwuEa/TUYn9CBVZYDMdn9III6hdDzVPKN/l5PE=; b=Yrzazy3T0CiGfi+wufycUrxE9XLSwtKeehpS+9cAJ4WsQdFOSnA6nVIBk37QV1vp80 3VpNaVG/7cA/851OVmzTPn3ORc+00N2jei/zlHNUtWaSCMTqQGfh7l+rZFr1OxWUTnMy Qv7fquFLA1gpT+ubsTab+d7HVYvAIKaytVfMt2ZuaCjUtYB5NZvpNhzka3bDw7X4KgpL OENGV/RXz6lO6+Wog0m8y1ZjwucAtvBEvHJWP1UGtjk//Nd1ekXVGnU/H5YCZrxWV5vh F7iSeY64Xv26/1rMpG2gkM9Gwd8q67DZKgSiaCRt2iIoOnP74y+5+bDBjZIgl94yDJNz NfEw== X-Gm-Message-State: AOAM530RgcT51bVkyPjh/qBHrLJ8OHyUJn2qmb/MUFEJwMi4xYFaajTG IFCZDiB3L6tEfUN8twrvMWTFC31eE84uP2QvwsHevCLtZvlbboTVejXPTP6kW6rji3EPVhZpYBK ujNK9+O38tHgunYaufX/O X-Received: by 2002:a17:906:fcc4:: with SMTP id qx4mr6751956ejb.42.1617966781264; Fri, 09 Apr 2021 04:13:01 -0700 (PDT) X-Google-Smtp-Source: ABdhPJyN01aC0ArployKcFNzWC+455t509jtFprEos2SXUsaUxRWFCvmE9PBB5j0Mfpph1bCkHvNIw== X-Received: by 2002:a17:906:fcc4:: with SMTP id qx4mr6751940ejb.42.1617966781061; Fri, 09 Apr 2021 04:13:01 -0700 (PDT) Received: from localhost.localdomain ([2a02:8308:b105:dd00:277b:6436:24db:9466]) by smtp.gmail.com with ESMTPSA id w18sm1046854ejq.58.2021.04.09.04.12.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 09 Apr 2021 04:13:00 -0700 (PDT) From: Ondrej Mosnacek To: linux-security-module@vger.kernel.org, selinux@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-btrfs@vger.kernel.org, Paul Moore , Olga Kornievskaia , Al Viro , David Howells , Stephen Smalley Subject: [PATCH 2/2] selinux: fix SECURITY_LSM_NATIVE_LABELS flag handling on double mount Date: Fri, 9 Apr 2021 13:12:54 +0200 Message-Id: <20210409111254.271800-3-omosnace@redhat.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210409111254.271800-1-omosnace@redhat.com> References: <20210409111254.271800-1-omosnace@redhat.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org When mounting an NFS export that is a mountpoint on the host, doing the same mount a second time leads to a security_sb_set_mnt_opts() call on an already intialized superblock, which leaves the SECURITY_LSM_NATIVE_LABELS flag unset even if it's provided by the FS. NFS then obediently clears NFS_CAP_SECURITY_LABEL from its server capability set, leading to any newly created inodes for this superblock to end up without labels. To fix this, make sure to return the SECURITY_LSM_NATIVE_LABELS flag when security_sb_set_mnt_opts() is called on an already initialized superblock with matching security options. While there, also do a sanity check to ensure that SECURITY_LSM_NATIVE_LABELS is set in kflags if and only if sbsec->behavior == SECURITY_FS_USE_NATIVE. Minimal reproducer: # systemctl start nfs-server # exportfs -o rw,no_root_squash,security_label localhost:/ # mount -t nfs -o "nfsvers=4.2" localhost:/etc /mnt # mount -t nfs -o "nfsvers=4.2" localhost:/etc /mnt # ls -lZ /mnt [all labels are system_u:object_r:unlabeled_t:s0] Signed-off-by: Ondrej Mosnacek --- security/selinux/hooks.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 1daf7bec4bb0..b8efb14a1d1a 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -741,7 +741,24 @@ static int selinux_set_mnt_opts(struct super_block *sb, /* previously mounted with options, but not on this attempt? */ if ((sbsec->flags & SE_MNTMASK) && !opts) goto out_double_mount; + + /* + * If we are checking an already initialized mount and the + * options match, make sure to return back the + * SECURITY_LSM_NATIVE_LABELS flag if applicable. If the + * superblock has the NATIVE behavior set and the FS is not + * signaling its support (or vice versa), then it is a + * programmer error, so emit a WARNING and return -EINVAL. + */ rc = 0; + if (sbsec->behavior == SECURITY_FS_USE_NATIVE) { + if (WARN_ON(!(kern_flags & SECURITY_LSM_NATIVE_LABELS))) + rc = -EINVAL; + else + *set_kern_flags |= SECURITY_LSM_NATIVE_LABELS; + } else if (WARN_ON(kern_flags & SECURITY_LSM_NATIVE_LABELS)) { + rc = -EINVAL; + } goto out; }