From patchwork Mon Sep 26 14:08:20 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Brauner X-Patchwork-Id: 12988923 X-Patchwork-Delegate: paul@paul-moore.com 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 20306C32771 for ; Mon, 26 Sep 2022 15:24:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236360AbiIZPYv (ORCPT ); Mon, 26 Sep 2022 11:24:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49374 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236679AbiIZPYB (ORCPT ); Mon, 26 Sep 2022 11:24:01 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8C4231055B; Mon, 26 Sep 2022 07:09:42 -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 dfw.source.kernel.org (Postfix) with ESMTPS id 21EE460DD6; Mon, 26 Sep 2022 14:09:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 54B13C43141; Mon, 26 Sep 2022 14:09:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1664201381; bh=fLZ0ssJpiRYGlLTGj4YAxLoCn2VGazr7CmAEgwtaBqk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=paMecCwaxFv3834BrIxgDYBdowuiUhGQlQtAWW24oOmCgnj5AYuBvEZQl3diamQ1J FZHdKb7XHcuvXGX9ECtg3w4Waz/jGgFz3VP9/YtAx3QjXpHw9BeHOx5kq1AyHcW/rj TQh+Y33JzgtMnL+MYfYSeoZruUVNgosNluVxYAsvzL6D2kebHKvO76gsN1QXMfartb XnQfXaGld5nfXdsyKhd4LdAcU0ssHfIqZUwEbFKWjYIWvCBAZuOdoFK1YqtlKDAX9G Fo9ZB72w64CUzEhD2rtDajfpXPKjrMROKwV2azlLYVh9mNUIch+bYh05pHcPIcovHD OiLiN3/Ig/MJQ== From: Christian Brauner To: linux-fsdevel@vger.kernel.org Cc: Christian Brauner , Seth Forshee , Christoph Hellwig , Al Viro , Miklos Szeredi , Amir Goldstein , linux-unionfs@vger.kernel.org, linux-security-module@vger.kernel.org Subject: [PATCH v2 23/30] ovl: implement set acl method Date: Mon, 26 Sep 2022 16:08:20 +0200 Message-Id: <20220926140827.142806-24-brauner@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220926140827.142806-1-brauner@kernel.org> References: <20220926140827.142806-1-brauner@kernel.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=7696; i=brauner@kernel.org; h=from:subject; bh=fLZ0ssJpiRYGlLTGj4YAxLoCn2VGazr7CmAEgwtaBqk=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMSQbbnISvBIhEtWinaOqde7ry5kzs28KMVkdLYxLLOTbeOnM UbG6jlIWBjEuBlkxRRaHdpNwueU8FZuNMjVg5rAygQxh4OIUgImca2T4zVIuslzjjCvP2o+ObcXf1+ k6Wux53+4V71bm4lxckn3sPSPDDl/vgxmXJxX8mfSnef7vmilvAnmL/L60tofYRH+oPePPBwA= X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Precedence: bulk List-ID: The current way of setting and getting posix acls through the generic xattr interface is error prone and type unsafe. The vfs needs to interpret and fixup posix acls before storing or reporting it to userspace. Various hacks exist to make this work. The code is hard to understand and difficult to maintain in it's current form. Instead of making this work by hacking posix acls through xattr handlers we are building a dedicated posix acl api around the get and set inode operations. This removes a lot of hackiness and makes the codepaths easier to maintain. A lot of background can be found in [1]. In order to build a type safe posix api around get and set acl we need all filesystem to implement get and set acl. Now that we have added get and set acl inode operations that allow easy access to the dentry we give overlayfs it's own get and set acl inode operations. The set acl inode operation is duplicates most of the ovl posix acl xattr handler. The main difference being that the set acl inode operation relies on the new posix acl api. Once the vfs has been switched over the custom posix acl xattr handler will be removed completely. Note, until the vfs has been switched to the new posix acl api this patch is a non-functional change. Link: https://lore.kernel.org/all/20220801145520.1532837-1-brauner@kernel.org [1] Signed-off-by: Christian Brauner (Microsoft) --- Notes: /* v2 */ Miklos Szeredi : - split ovl_set_acl() into two functions - add comment about checking whether copy up is even necessary fs/overlayfs/dir.c | 1 + fs/overlayfs/inode.c | 94 ++++++++++++++++++++++++++++++++++++++++ fs/overlayfs/overlayfs.h | 17 ++++++++ 3 files changed, 112 insertions(+) diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c index eb49d5d7b56f..0e817ebce92c 100644 --- a/fs/overlayfs/dir.c +++ b/fs/overlayfs/dir.c @@ -1313,6 +1313,7 @@ const struct inode_operations ovl_dir_inode_operations = { .listxattr = ovl_listxattr, .get_inode_acl = ovl_get_inode_acl, .get_acl = ovl_get_acl, + .set_acl = ovl_set_acl, .update_time = ovl_update_time, .fileattr_get = ovl_fileattr_get, .fileattr_set = ovl_fileattr_set, diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c index fed72225ebe1..fc4c2d821343 100644 --- a/fs/overlayfs/inode.c +++ b/fs/overlayfs/inode.c @@ -594,6 +594,98 @@ struct posix_acl *ovl_get_acl(struct user_namespace *mnt_userns, revert_creds(old_cred); return acl; } + +static int ovl_set_or_remove_acl(struct dentry *dentry, struct inode *inode, + struct posix_acl *acl, int type) +{ + int err; + struct path realpath; + const char *acl_name; + const struct cred *old_cred; + struct ovl_fs *ofs = OVL_FS(dentry->d_sb); + struct dentry *upperdentry = ovl_dentry_upper(dentry); + struct dentry *realdentry = upperdentry ?: ovl_dentry_lower(dentry); + + err = ovl_want_write(dentry); + if (err) + return err; + + /* + * If ACL is to be removed from a lower file, check if it exists in + * the first place before copying it up. + */ + acl_name = posix_acl_xattr_name(type); + if (!acl && !upperdentry) { + struct posix_acl *real_acl; + + ovl_path_lower(dentry, &realpath); + old_cred = ovl_override_creds(dentry->d_sb); + real_acl = vfs_get_acl(mnt_user_ns(realpath.mnt), realdentry, + acl_name); + revert_creds(old_cred); + posix_acl_release(real_acl); + if (IS_ERR(real_acl)) { + err = PTR_ERR(real_acl); + goto out_drop_write; + } + } + + if (!upperdentry) { + err = ovl_copy_up(dentry); + if (err) + goto out_drop_write; + + realdentry = ovl_dentry_upper(dentry); + } + + old_cred = ovl_override_creds(dentry->d_sb); + if (acl) + err = ovl_do_set_acl(ofs, realdentry, acl_name, acl); + else + err = ovl_do_remove_acl(ofs, realdentry, acl_name); + revert_creds(old_cred); + + /* copy c/mtime */ + ovl_copyattr(inode); + +out_drop_write: + ovl_drop_write(dentry); + return err; +} + +int ovl_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry, + struct posix_acl *acl, int type) +{ + int err; + struct inode *inode = d_inode(dentry); + struct dentry *workdir = ovl_workdir(dentry); + struct inode *realinode = ovl_inode_real(inode); + + if (!IS_POSIXACL(d_inode(workdir))) + return -EOPNOTSUPP; + if (!realinode->i_op->set_acl) + return -EOPNOTSUPP; + if (type == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) + return acl ? -EACCES : 0; + if (!inode_owner_or_capable(&init_user_ns, inode)) + return -EPERM; + + /* + * Check if sgid bit needs to be cleared (actual setacl operation will + * be done with mounter's capabilities and so that won't do it for us). + */ + if (unlikely(inode->i_mode & S_ISGID) && type == ACL_TYPE_ACCESS && + !in_group_p(inode->i_gid) && + !capable_wrt_inode_uidgid(&init_user_ns, inode, CAP_FSETID)) { + struct iattr iattr = { .ia_valid = ATTR_KILL_SGID }; + + err = ovl_setattr(&init_user_ns, dentry, &iattr); + if (err) + return err; + } + + return ovl_set_or_remove_acl(dentry, inode, acl, type); +} #endif int ovl_update_time(struct inode *inode, struct timespec64 *ts, int flags) @@ -770,6 +862,7 @@ static const struct inode_operations ovl_file_inode_operations = { .listxattr = ovl_listxattr, .get_inode_acl = ovl_get_inode_acl, .get_acl = ovl_get_acl, + .set_acl = ovl_set_acl, .update_time = ovl_update_time, .fiemap = ovl_fiemap, .fileattr_get = ovl_fileattr_get, @@ -791,6 +884,7 @@ static const struct inode_operations ovl_special_inode_operations = { .listxattr = ovl_listxattr, .get_inode_acl = ovl_get_inode_acl, .get_acl = ovl_get_acl, + .set_acl = ovl_set_acl, .update_time = ovl_update_time, }; diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h index 68a3030332e9..b2645baeba2f 100644 --- a/fs/overlayfs/overlayfs.h +++ b/fs/overlayfs/overlayfs.h @@ -8,6 +8,8 @@ #include #include #include +#include +#include #include "ovl_entry.h" #undef pr_fmt @@ -278,6 +280,18 @@ static inline int ovl_removexattr(struct ovl_fs *ofs, struct dentry *dentry, return ovl_do_removexattr(ofs, dentry, ovl_xattr(ofs, ox)); } +static inline int ovl_do_set_acl(struct ovl_fs *ofs, struct dentry *dentry, + const char *acl_name, struct posix_acl *acl) +{ + return vfs_set_acl(ovl_upper_mnt_userns(ofs), dentry, acl_name, acl); +} + +static inline int ovl_do_remove_acl(struct ovl_fs *ofs, struct dentry *dentry, + const char *acl_name) +{ + return vfs_remove_acl(ovl_upper_mnt_userns(ofs), dentry, acl_name); +} + static inline int ovl_do_rename(struct ovl_fs *ofs, struct inode *olddir, struct dentry *olddentry, struct inode *newdir, struct dentry *newdentry, unsigned int flags) @@ -595,12 +609,15 @@ ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size); struct posix_acl *ovl_get_inode_acl(struct inode *inode, int type, bool rcu); struct posix_acl *ovl_get_acl(struct user_namespace *mnt_userns, struct dentry *dentry, int type); +int ovl_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry, + struct posix_acl *acl, int type); void ovl_idmap_posix_acl(struct inode *realinode, struct user_namespace *mnt_userns, struct posix_acl *acl); #else #define ovl_get_inode_acl NULL #define ovl_get_acl NULL +#define ovl_set_acl NULL #endif int ovl_update_time(struct inode *inode, struct timespec64 *ts, int flags);