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 146F1C76195 for ; Mon, 20 Mar 2023 15:16:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232388AbjCTPQn (ORCPT ); Mon, 20 Mar 2023 11:16:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48560 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232317AbjCTPQX (ORCPT ); Mon, 20 Mar 2023 11:16:23 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CF0F930B34 for ; Mon, 20 Mar 2023 08:11:28 -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 ams.source.kernel.org (Postfix) with ESMTPS id BAE59B80EAC for ; Mon, 20 Mar 2023 15:11:27 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 31301C4339B; Mon, 20 Mar 2023 15:11:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1679325086; bh=45wYGTHCdsXSviCNcEC6OkQbfhmqAxBGQPi2KM9LsSc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=zAcfJYyvGfT6rtrV2PQXFmXfs2sliehPPbG+AR6mJx/WFxLefVxSUpiARV44IXdvK 5/FnsBx3zcl1sXBN3SjvNaxCu1BBTSk372js3g5y9MD5Azv4jIrw/f+YHHy/m9yWTA fmsh5DqbYgV41ricfQnCQ0Wn9gWzq99pXUrNuBPo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Darrick J. Wong" , "Christian Brauner (Microsoft)" , Yang Xu , Amir Goldstein , Jeff Layton Subject: [PATCH 5.10 90/99] fs: add mode_strip_sgid() helper Date: Mon, 20 Mar 2023 15:55:08 +0100 Message-Id: <20230320145447.175059260@linuxfoundation.org> X-Mailer: git-send-email 2.40.0 In-Reply-To: <20230320145443.333824603@linuxfoundation.org> References: <20230320145443.333824603@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: Yang Xu commit 2b3416ceff5e6bd4922f6d1c61fb68113dd82302 upstream. [remove userns argument of helper for 5.10.y backport] Add a dedicated helper to handle the setgid bit when creating a new file in a setgid directory. This is a preparatory patch for moving setgid stripping into the vfs. The patch contains no functional changes. Currently the setgid stripping logic is open-coded directly in inode_init_owner() and the individual filesystems are responsible for handling setgid inheritance. Since this has proven to be brittle as evidenced by old issues we uncovered over the last months (see [1] to [3] below) we will try to move this logic into the vfs. Link: e014f37db1a2 ("xfs: use setattr_copy to set vfs inode attributes") [1] Link: 01ea173e103e ("xfs: fix up non-directory creation in SGID directories") [2] Link: fd84bfdddd16 ("ceph: fix up non-directory creation in SGID directories") [3] Link: https://lore.kernel.org/r/1657779088-2242-1-git-send-email-xuyang2018.jy@fujitsu.com Reviewed-by: Darrick J. Wong Reviewed-by: Christian Brauner (Microsoft) Reviewed-and-Tested-by: Jeff Layton Signed-off-by: Yang Xu Signed-off-by: Christian Brauner (Microsoft) Signed-off-by: Amir Goldstein Signed-off-by: Greg Kroah-Hartman --- fs/inode.c | 34 ++++++++++++++++++++++++++++++---- include/linux/fs.h | 1 + 2 files changed, 31 insertions(+), 4 deletions(-) --- a/fs/inode.c +++ b/fs/inode.c @@ -2147,10 +2147,8 @@ void inode_init_owner(struct inode *inod /* Directories are special, and always inherit S_ISGID */ if (S_ISDIR(mode)) mode |= S_ISGID; - else if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP) && - !in_group_p(inode->i_gid) && - !capable_wrt_inode_uidgid(dir, CAP_FSETID)) - mode &= ~S_ISGID; + else + mode = mode_strip_sgid(dir, mode); } else inode->i_gid = current_fsgid(); inode->i_mode = mode; @@ -2382,3 +2380,31 @@ int vfs_ioc_fssetxattr_check(struct inod return 0; } EXPORT_SYMBOL(vfs_ioc_fssetxattr_check); + +/** + * mode_strip_sgid - handle the sgid bit for non-directories + * @dir: parent directory inode + * @mode: mode of the file to be created in @dir + * + * If the @mode of the new file has both the S_ISGID and S_IXGRP bit + * raised and @dir has the S_ISGID bit raised ensure that the caller is + * either in the group of the parent directory or they have CAP_FSETID + * in their user namespace and are privileged over the parent directory. + * In all other cases, strip the S_ISGID bit from @mode. + * + * Return: the new mode to use for the file + */ +umode_t mode_strip_sgid(const struct inode *dir, umode_t mode) +{ + if ((mode & (S_ISGID | S_IXGRP)) != (S_ISGID | S_IXGRP)) + return mode; + if (S_ISDIR(mode) || !dir || !(dir->i_mode & S_ISGID)) + return mode; + if (in_group_p(dir->i_gid)) + return mode; + if (capable_wrt_inode_uidgid(dir, CAP_FSETID)) + return mode; + + return mode & ~S_ISGID; +} +EXPORT_SYMBOL(mode_strip_sgid); --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1768,6 +1768,7 @@ extern long compat_ptr_ioctl(struct file extern void inode_init_owner(struct inode *inode, const struct inode *dir, umode_t mode); extern bool may_open_dev(const struct path *path); +umode_t mode_strip_sgid(const struct inode *dir, umode_t mode); /* * This is the "filldir" function type, used by readdir() to let