From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752098Ab2KSKu6 (ORCPT ); Mon, 19 Nov 2012 05:50:58 -0500 Received: from out03.mta.xmission.com ([166.70.13.233]:34084 "EHLO out03.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751871Ab2KSKuz (ORCPT ); Mon, 19 Nov 2012 05:50:55 -0500 From: "Eric W. Biederman" To: Cc: Linux Containers , , Al Viro , "Eric W. Biederman" Date: Mon, 19 Nov 2012 02:50:21 -0800 Message-Id: <1353322222-27060-5-git-send-email-ebiederm@xmission.com> X-Mailer: git-send-email 1.7.5.4 In-Reply-To: <1353322222-27060-1-git-send-email-ebiederm@xmission.com> References: <87k3thc1h3.fsf@xmission.com> <1353322222-27060-1-git-send-email-ebiederm@xmission.com> X-XM-AID: U2FsdGVkX18m0k0C7F4wV6Nmh5JdIZykR/2JIvalpP0= X-SA-Exim-Connect-IP: 98.207.153.68 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.1 XMSubLong Long Subject * 0.0 T_TM2_M_HEADER_IN_MSG BODY: T_TM2_M_HEADER_IN_MSG * -3.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% * [score: 0.0000] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa07 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 T_TooManySym_01 4+ unique symbols in subject * 0.0 T_XMDrugObfuBody_08 obfuscated drug references X-Spam-DCC: XMission; sa07 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ; X-Spam-Relay-Country: Subject: [PATCH review 5/6] vfs: Allow unprivileged manipulation of the mount namespace. X-SA-Exim-Version: 4.2.1 (built Sun, 08 Jan 2012 03:05:19 +0000) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Eric W. Biederman" - Add a filesystem flag to mark filesystems that are safe to mount as an unprivileged user. - Add a filesystem flag to mark filesystems that don't need MNT_NODEV when mounted by an unprivileged user. - Relax the permission checks to allow unprivileged users that have CAP_SYS_ADMIN permissions in the user namespace referred to by the current mount namespace to be allowed to mount, unmount, and move filesystems. Acked-by: "Serge E. Hallyn" Signed-off-by: "Eric W. Biederman" --- fs/namespace.c | 69 ++++++++++++++++++++++++++++++++------------------- include/linux/fs.h | 2 + 2 files changed, 45 insertions(+), 26 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index 4dfcaf0..9ddc86f 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1269,7 +1269,7 @@ SYSCALL_DEFINE2(umount, char __user *, name, int, flags) goto dput_and_out; retval = -EPERM; - if (!capable(CAP_SYS_ADMIN)) + if (!ns_capable(mnt->mnt_ns->user_ns, CAP_SYS_ADMIN)) goto dput_and_out; retval = do_umount(mnt, flags); @@ -1295,7 +1295,7 @@ SYSCALL_DEFINE1(oldumount, char __user *, name) static int mount_is_safe(struct path *path) { - if (capable(CAP_SYS_ADMIN)) + if (ns_capable(real_mount(path->mnt)->mnt_ns->user_ns, CAP_SYS_ADMIN)) return 0; return -EPERM; #ifdef notyet @@ -1633,7 +1633,7 @@ static int do_change_type(struct path *path, int flag) int type; int err = 0; - if (!capable(CAP_SYS_ADMIN)) + if (!ns_capable(mnt->mnt_ns->user_ns, CAP_SYS_ADMIN)) return -EPERM; if (path->dentry != path->mnt->mnt_root) @@ -1797,7 +1797,7 @@ static int do_move_mount(struct path *path, const char *old_name) struct mount *p; struct mount *old; int err = 0; - if (!capable(CAP_SYS_ADMIN)) + if (!ns_capable(real_mount(path->mnt)->mnt_ns->user_ns, CAP_SYS_ADMIN)) return -EPERM; if (!old_name || !*old_name) return -EINVAL; @@ -1884,21 +1884,6 @@ static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype) return ERR_PTR(err); } -static struct vfsmount * -do_kern_mount(const char *fstype, int flags, const char *name, void *data) -{ - struct file_system_type *type = get_fs_type(fstype); - struct vfsmount *mnt; - if (!type) - return ERR_PTR(-ENODEV); - mnt = vfs_kern_mount(type, flags, name, data); - if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) && - !mnt->mnt_sb->s_subtype) - mnt = fs_set_subtype(mnt, fstype); - put_filesystem(type); - return mnt; -} - /* * add a mount into a namespace's mount tree */ @@ -1944,20 +1929,46 @@ unlock: * create a new mount for userspace and request it to be added into the * namespace's tree */ -static int do_new_mount(struct path *path, const char *type, int flags, +static int do_new_mount(struct path *path, const char *fstype, int flags, int mnt_flags, const char *name, void *data) { + struct file_system_type *type; + struct user_namespace *user_ns; struct vfsmount *mnt; int err; - if (!type) + if (!fstype) return -EINVAL; /* we need capabilities... */ - if (!capable(CAP_SYS_ADMIN)) + user_ns = real_mount(path->mnt)->mnt_ns->user_ns; + if (!ns_capable(user_ns, CAP_SYS_ADMIN)) return -EPERM; - mnt = do_kern_mount(type, flags, name, data); + type = get_fs_type(fstype); + if (!type) + return -ENODEV; + + if (user_ns != &init_user_ns) { + if (!(type->fs_flags & FS_USERNS_MOUNT)) { + put_filesystem(type); + return -EPERM; + } + /* Only in special cases allow devices from mounts + * created outside the initial user namespace. + */ + if (!(type->fs_flags & FS_USERNS_DEV_MOUNT)) { + flags |= MS_NODEV; + mnt_flags |= MNT_NODEV; + } + } + + mnt = vfs_kern_mount(type, flags, name, data); + if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) && + !mnt->mnt_sb->s_subtype) + mnt = fs_set_subtype(mnt, fstype); + + put_filesystem(type); if (IS_ERR(mnt)) return PTR_ERR(mnt); @@ -2549,7 +2560,7 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, struct mount *new_mnt, *root_mnt; int error; - if (!capable(CAP_SYS_ADMIN)) + if (!ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN)) return -EPERM; error = user_path_dir(new_root, &new); @@ -2631,8 +2642,13 @@ static void __init init_mount_tree(void) struct vfsmount *mnt; struct mnt_namespace *ns; struct path root; + struct file_system_type *type; - mnt = do_kern_mount("rootfs", 0, "rootfs", NULL); + type = get_fs_type("rootfs"); + if (!type) + panic("Can't find rootfs type"); + mnt = vfs_kern_mount(type, 0, "rootfs", NULL); + put_filesystem(type); if (IS_ERR(mnt)) panic("Can't create rootfs"); @@ -2757,7 +2773,8 @@ static int mntns_install(struct nsproxy *nsproxy, void *ns) struct mnt_namespace *mnt_ns = ns; struct path root; - if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_CHROOT)) + if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) || + !nsown_capable(CAP_SYS_CHROOT)) return -EINVAL; if (fs->users != 1) diff --git a/include/linux/fs.h b/include/linux/fs.h index b33cfc9..5037aa6 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1812,6 +1812,8 @@ struct file_system_type { #define FS_REQUIRES_DEV 1 #define FS_BINARY_MOUNTDATA 2 #define FS_HAS_SUBTYPE 4 +#define FS_USERNS_MOUNT 8 /* Can be mounted by userns root */ +#define FS_USERNS_DEV_MOUNT 16 /* A userns mount does not imply MNT_NODEV */ #define FS_REVAL_DOT 16384 /* Check the paths ".", ".." for staleness */ #define FS_RENAME_DOES_D_MOVE 32768 /* FS will handle d_move() during rename() internally. */ struct dentry *(*mount) (struct file_system_type *, int, -- 1.7.5.4