From patchwork Thu Dec 3 23:57:30 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Christian Brauner X-Patchwork-Id: 11950235 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=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 77936C2BBCA for ; Fri, 4 Dec 2020 00:13:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 26615222B6 for ; Fri, 4 Dec 2020 00:13:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2502159AbgLDANT (ORCPT ); Thu, 3 Dec 2020 19:13:19 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:43400 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2502147AbgLDANS (ORCPT ); Thu, 3 Dec 2020 19:13:18 -0500 Received: from ip5f5af0a0.dynamic.kabel-deutschland.de ([95.90.240.160] helo=wittgenstein.fritz.box) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1kkyYC-0007ka-U4; Fri, 04 Dec 2020 00:02:17 +0000 From: Christian Brauner To: Alexander Viro , Christoph Hellwig , linux-fsdevel@vger.kernel.org Cc: John Johansen , James Morris , Mimi Zohar , Dmitry Kasatkin , Stephen Smalley , Casey Schaufler , Arnd Bergmann , Andreas Dilger , OGAWA Hirofumi , Geoffrey Thomas , Mrunal Patel , Josh Triplett , Andy Lutomirski , Theodore Tso , Alban Crequy , Tycho Andersen , David Howells , James Bottomley , Seth Forshee , =?utf-8?q?St=C3=A9phane_Graber?= , Aleksa Sarai , Lennart Poettering , "Eric W. Biederman" , smbarber@chromium.org, Phil Estes , Serge Hallyn , Kees Cook , Todd Kjos , Paul Moore , Jonathan Corbet , containers@lists.linux-foundation.org, linux-security-module@vger.kernel.org, linux-api@vger.kernel.org, linux-ext4@vger.kernel.org, linux-integrity@vger.kernel.org, selinux@vger.kernel.org, Christian Brauner , Christoph Hellwig Subject: [PATCH v4 34/40] fat: handle idmapped mounts Date: Fri, 4 Dec 2020 00:57:30 +0100 Message-Id: <20201203235736.3528991-35-christian.brauner@ubuntu.com> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201203235736.3528991-1-christian.brauner@ubuntu.com> References: <20201203235736.3528991-1-christian.brauner@ubuntu.com> MIME-Version: 1.0 Precedence: bulk List-ID: Let fat handle idmapped mounts. This allows to have the same fat mount appear in multiple locations with different id mappings. This allows to expose a vfat formatted USB stick to multiple user with different ids on the host or in user namespaces allowing for dac permissions: mount -o uid=1000,gid=1000 /dev/sdb /mnt u1001@f2-vm:/lower1$ ls -ln /mnt/ total 4 -rwxr-xr-x 1 1000 1000 4 Oct 28 03:44 aaa -rwxr-xr-x 1 1000 1000 0 Oct 28 01:09 bbb -rwxr-xr-x 1 1000 1000 0 Oct 28 01:10 ccc -rwxr-xr-x 1 1000 1000 0 Oct 28 03:46 ddd -rwxr-xr-x 1 1000 1000 0 Oct 28 04:01 eee mount-idmapped --map-mount b:1000:1001:1 u1001@f2-vm:/lower1$ ls -ln /lower1/ total 4 -rwxr-xr-x 1 1001 1001 4 Oct 28 03:44 aaa -rwxr-xr-x 1 1001 1001 0 Oct 28 01:09 bbb -rwxr-xr-x 1 1001 1001 0 Oct 28 01:10 ccc -rwxr-xr-x 1 1001 1001 0 Oct 28 03:46 ddd -rwxr-xr-x 1 1001 1001 0 Oct 28 04:01 eee u1001@f2-vm:/lower1$ touch /lower1/fff u1001@f2-vm:/lower1$ ls -ln /lower1/fff -rwxr-xr-x 1 1001 1001 0 Oct 28 04:03 /lower1/fff u1001@f2-vm:/lower1$ ls -ln /mnt/fff -rwxr-xr-x 1 1000 1000 0 Oct 28 04:03 /mnt/fff Cc: Christoph Hellwig Cc: David Howells Cc: Al Viro Cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner --- /* v2 */ unchanged /* v3 */ unchanged /* v4 */ - Mauricio Vásquez Bernal : - Fix mount example in commit message. - Serge Hallyn : - Use "mnt_userns" to refer to a vfsmount's userns everywhere to make terminology consistent. --- fs/fat/file.c | 15 ++++++++------- fs/fat/namei_msdos.c | 2 +- fs/fat/namei_vfat.c | 2 +- 3 files changed, 10 insertions(+), 9 deletions(-) diff --git a/fs/fat/file.c b/fs/fat/file.c index 73acd0843d92..6a618e9450c8 100644 --- a/fs/fat/file.c +++ b/fs/fat/file.c @@ -398,7 +398,7 @@ int fat_getattr(struct user_namespace *mnt_userns, const struct path *path, struct kstat *stat, u32 request_mask, unsigned int flags) { struct inode *inode = d_inode(path->dentry); - generic_fillattr(&init_user_ns, inode, stat); + generic_fillattr(mnt_userns, inode, stat); stat->blksize = MSDOS_SB(inode->i_sb)->cluster_size; if (MSDOS_SB(inode->i_sb)->options.nfs == FAT_NFS_NOSTALE_RO) { @@ -447,12 +447,13 @@ static int fat_sanitize_mode(const struct msdos_sb_info *sbi, return 0; } -static int fat_allow_set_time(struct msdos_sb_info *sbi, struct inode *inode) +static int fat_allow_set_time(struct user_namespace *mnt_userns, + struct msdos_sb_info *sbi, struct inode *inode) { umode_t allow_utime = sbi->options.allow_utime; - if (!uid_eq(current_fsuid(), inode->i_uid)) { - if (in_group_p(inode->i_gid)) + if (!uid_eq(current_fsuid(), i_uid_into_mnt(mnt_userns, inode))) { + if (in_group_p(i_gid_into_mnt(mnt_userns, inode))) allow_utime >>= 3; if (allow_utime & MAY_WRITE) return 1; @@ -477,11 +478,11 @@ int fat_setattr(struct user_namespace *mnt_userns, struct dentry *dentry, /* Check for setting the inode time. */ ia_valid = attr->ia_valid; if (ia_valid & TIMES_SET_FLAGS) { - if (fat_allow_set_time(sbi, inode)) + if (fat_allow_set_time(mnt_userns, sbi, inode)) attr->ia_valid &= ~TIMES_SET_FLAGS; } - error = setattr_prepare(&init_user_ns, dentry, attr); + error = setattr_prepare(mnt_userns, dentry, attr); attr->ia_valid = ia_valid; if (error) { if (sbi->options.quiet) @@ -551,7 +552,7 @@ int fat_setattr(struct user_namespace *mnt_userns, struct dentry *dentry, fat_truncate_time(inode, &attr->ia_mtime, S_MTIME); attr->ia_valid &= ~(ATTR_ATIME|ATTR_CTIME|ATTR_MTIME); - setattr_copy(&init_user_ns, inode, attr); + setattr_copy(mnt_userns, inode, attr); mark_inode_dirty(inode); out: return error; diff --git a/fs/fat/namei_msdos.c b/fs/fat/namei_msdos.c index a8f3375d9d10..efba301d68ae 100644 --- a/fs/fat/namei_msdos.c +++ b/fs/fat/namei_msdos.c @@ -667,7 +667,7 @@ static struct file_system_type msdos_fs_type = { .name = "msdos", .mount = msdos_mount, .kill_sb = kill_block_super, - .fs_flags = FS_REQUIRES_DEV, + .fs_flags = FS_REQUIRES_DEV | FS_ALLOW_IDMAP, }; MODULE_ALIAS_FS("msdos"); diff --git a/fs/fat/namei_vfat.c b/fs/fat/namei_vfat.c index 23936ecf79a5..5369d82e0bfb 100644 --- a/fs/fat/namei_vfat.c +++ b/fs/fat/namei_vfat.c @@ -1063,7 +1063,7 @@ static struct file_system_type vfat_fs_type = { .name = "vfat", .mount = vfat_mount, .kill_sb = kill_block_super, - .fs_flags = FS_REQUIRES_DEV, + .fs_flags = FS_REQUIRES_DEV | FS_ALLOW_IDMAP, }; MODULE_ALIAS_FS("vfat");