From patchwork Thu Sep 12 13:30:07 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jonathan Lebon X-Patchwork-Id: 11143083 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id E3E641599 for ; Thu, 12 Sep 2019 13:30:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CBE9820830 for ; Thu, 12 Sep 2019 13:30:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732192AbfILNaj (ORCPT ); Thu, 12 Sep 2019 09:30:39 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52278 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731687AbfILNaj (ORCPT ); Thu, 12 Sep 2019 09:30:39 -0400 Received: from mail-qt1-f197.google.com (mail-qt1-f197.google.com [209.85.160.197]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 97CC359465 for ; Thu, 12 Sep 2019 13:30:38 +0000 (UTC) Received: by mail-qt1-f197.google.com with SMTP id c8so13609684qtd.20 for ; Thu, 12 Sep 2019 06:30:38 -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:mime-version :content-transfer-encoding; bh=S/MIBrjCy5DTvfqPzJTJqDQQH1pDu780wgGyHs56w4k=; b=H7fZr4X/c4ge0SXeHHRXrq3U4J60PWfSRqdCphTWxKjyLvBs8nktbJczT562oH7Hxv hdvVjKgAzNxIXFdQetnmveDXojtHFrE21PNdo5ONQIyh35oZyrJB4ewZdUrNfbrvDc2y ElMr/HoKEX5pY+GMJE4nzeBotlfCWU9BoAxJPUhzKA9Oib+AqDzQ0hCGH6pQY9RXRXBV IMH21FE5dxQGtLHNCJXVxE14edDeRo8qQFWQw6ooogK7JvduuJrWBn3BmCbKz1YLTNZE 9wRXvaHFVGNhr79JrRcItTp6Sx+tZ3XY46CV+Wi6Rq1fu8MePP9zFdIQXw9wqyd+UgLa AIlw== X-Gm-Message-State: APjAAAXpWx500L+bZRH8M7OzuSb0aBlsvvjaBYCGvSkzojpa2nRWjtk0 cjKEj45ivsUgPW2Bbi6CGEtspqM4wmwb72z+ajR4hy5OjMT3KRh6W71HFbVPrlLYQTvse11Ax2d wGOma7U/qIGDDYkjh/Q== X-Received: by 2002:ac8:7b2e:: with SMTP id l14mr8094193qtu.11.1568295037636; Thu, 12 Sep 2019 06:30:37 -0700 (PDT) X-Google-Smtp-Source: APXvYqzybFpoaFyGZXafGEdtHCL3XllpHltaXggcIZEb7De49V/kJzm1pU6vpg1gN8HtgnB3cilLuA== X-Received: by 2002:ac8:7b2e:: with SMTP id l14mr8094176qtu.11.1568295037442; Thu, 12 Sep 2019 06:30:37 -0700 (PDT) Received: from localhost.localdomain ([12.133.141.2]) by smtp.gmail.com with ESMTPSA id h68sm11848865qkd.35.2019.09.12.06.30.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Sep 2019 06:30:36 -0700 (PDT) From: Jonathan Lebon To: selinux@vger.kernel.org Cc: Jonathan Lebon , Victor Kamensky Subject: [PATCH v2] selinux: allow labeling before policy is loaded Date: Thu, 12 Sep 2019 09:30:07 -0400 Message-Id: <20190912133007.27545-1-jlebon@redhat.com> X-Mailer: git-send-email 2.21.0 MIME-Version: 1.0 Sender: selinux-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: selinux@vger.kernel.org Currently, the SELinux LSM prevents one from setting the `security.selinux` xattr on an inode without a policy first being loaded. However, this restriction is problematic: it makes it impossible to have newly created files with the correct label before actually loading the policy. This is relevant in distributions like Fedora, where the policy is loaded by systemd shortly after pivoting out of the initrd. In such instances, all files created prior to pivoting will be unlabeled. One then has to relabel them after pivoting, an operation which inherently races with other processes trying to access those same files. Going further, there are use cases for creating the entire root filesystem on first boot from the initrd (e.g. Container Linux supports this today[1], and we'd like to support it in Fedora CoreOS as well[2]). One can imagine doing this in two ways: at the block device level (e.g. laying down a disk image), or at the filesystem level. In the former, labeling can simply be part of the image. But even in the latter scenario, one still really wants to be able to set the right labels when populating the new filesystem. This patch enables this by changing behaviour in the following two ways: 1. allow `setxattr` if we're not initialized 2. don't try to set the in-core inode SID if we're not initialized; instead leave it as `LABEL_INVALID` so that revalidation may be attempted at a later time Note the first hunk of this patch is mostly the same as a previously discussed one[3], though it was part of a larger series which wasn't accepted. Co-developed-by: Victor Kamensky Signed-off-by: Victor Kamensky Signed-off-by: Jonathan Lebon [1] https://coreos.com/os/docs/latest/root-filesystem-placement.html [2] https://github.com/coreos/fedora-coreos-tracker/issues/94 [3] https://www.spinics.net/lists/linux-initramfs/msg04593.html --- v2: - return early in selinux_inode_setxattr if policy hasn't been loaded --- security/selinux/hooks.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 94de51628..dbe96c707 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -3142,6 +3142,9 @@ static int selinux_inode_setxattr(struct dentry *dentry, const char *name, return dentry_has_perm(current_cred(), dentry, FILE__SETATTR); } + if (!selinux_state.initialized) + return (inode_owner_or_capable(inode) ? 0 : -EPERM); + sbsec = inode->i_sb->s_security; if (!(sbsec->flags & SBLABEL_MNT)) return -EOPNOTSUPP; @@ -3225,6 +3228,15 @@ static void selinux_inode_post_setxattr(struct dentry *dentry, const char *name, return; } + if (!selinux_state.initialized) { + /* If we haven't even been initialized, then we can't validate + * against a policy, so leave the label as invalid. It may + * resolve to a valid label on the next revalidation try if + * we've since initialized. + */ + return; + } + rc = security_context_to_sid_force(&selinux_state, value, size, &newsid); if (rc) {