Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:36876 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933118AbdEKOBE (ORCPT ); Thu, 11 May 2017 10:01:04 -0400 Subject: [PATCH 08/14] Implement fsmount() to effect a pre-configured mount [ver #2] From: David Howells To: mszeredi@redhat.com, viro@zeniv.linux.org.uk, jlayton@redhat.com Cc: dhowells@redhat.com, linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org Date: Thu, 11 May 2017 15:01:00 +0100 Message-ID: <149451126044.4599.15065000638005379027.stgit@warthog.procyon.org.uk> In-Reply-To: <149451118535.4599.16084557087363834548.stgit@warthog.procyon.org.uk> References: <149451118535.4599.16084557087363834548.stgit@warthog.procyon.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Sender: linux-nfs-owner@vger.kernel.org List-ID: Provide a system call by which a filesystem opened with fsopen() and configured by a series of writes can be mounted: int ret = fsmount(int fsfd, int dfd, const char *path, unsigned int at_flags, unsigned int flags); where fsfd is the fd returned by fsopen(), dfd, path and at_flags locate the mountpoint and flags are the applicable MS_* flags. dfd can be AT_FDCWD or an fd open to a directory. In the event that fsmount() fails, it may be possible to get an error message by calling read(). If no message is available, ENODATA will be reported. Signed-off-by: David Howells --- arch/x86/entry/syscalls/syscall_32.tbl | 1 arch/x86/entry/syscalls/syscall_64.tbl | 1 fs/namespace.c | 99 ++++++++++++++++++++++++++++++++ include/linux/lsm_hooks.h | 6 ++ include/linux/security.h | 6 ++ include/linux/syscalls.h | 2 + kernel/sys_ni.c | 1 security/security.c | 7 ++ security/selinux/hooks.c | 13 ++++ 9 files changed, 136 insertions(+) diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl index 9bf8d4c62f85..abe6ea95e0e6 100644 --- a/arch/x86/entry/syscalls/syscall_32.tbl +++ b/arch/x86/entry/syscalls/syscall_32.tbl @@ -392,3 +392,4 @@ 383 i386 statx sys_statx 384 i386 arch_prctl sys_arch_prctl compat_sys_arch_prctl 385 i386 fsopen sys_fsopen +386 i386 fsmount sys_fsmount diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl index 9b198c5fc412..0977c5079831 100644 --- a/arch/x86/entry/syscalls/syscall_64.tbl +++ b/arch/x86/entry/syscalls/syscall_64.tbl @@ -340,6 +340,7 @@ 331 common pkey_free sys_pkey_free 332 common statx sys_statx 333 common fsopen sys_fsopen +334 common fsmount sys_fsmount # # x32-specific system call numbers start at 512 to avoid cache impact diff --git a/fs/namespace.c b/fs/namespace.c index 8ade7252ee34..6e43657d78bd 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -3253,6 +3253,105 @@ vfs_submount_sc(const struct dentry *mountpoint, struct sb_config *sc) EXPORT_SYMBOL_GPL(vfs_submount_sc); /* + * Mount a new, prepared superblock (specified by fs_fd) on the location + * specified by dfd and dir_name. dfd can be AT_FDCWD, a dir fd or a container + * fd. This cannot be used for binding, moving or remounting mounts. + */ +SYSCALL_DEFINE5(fsmount, int, fs_fd, int, dfd, const char __user *, dir_name, + unsigned int, at_flags, unsigned int, flags) +{ + struct sb_config *sc; + struct inode *inode; + struct path mountpoint; + struct fd f; + unsigned int lookup_flags, mnt_flags = 0; + long ret; + + if ((at_flags & ~(AT_SYMLINK_NOFOLLOW | AT_NO_AUTOMOUNT | + AT_EMPTY_PATH)) != 0) + return -EINVAL; + + if (flags & ~(MS_RDONLY | MS_NOSUID | MS_NODEV | MS_NOEXEC | + MS_NOATIME | MS_NODIRATIME | MS_RELATIME | MS_STRICTATIME)) + return -EINVAL; + + if (flags & MS_RDONLY) + mnt_flags |= MNT_READONLY; + if (flags & MS_NOSUID) + mnt_flags |= MNT_NOSUID; + if (flags & MS_NODEV) + mnt_flags |= MNT_NODEV; + if (flags & MS_NOEXEC) + mnt_flags |= MNT_NOEXEC; + if (flags & MS_NODIRATIME) + mnt_flags |= MNT_NODIRATIME; + + if (flags & MS_STRICTATIME) { + if (flags & MS_NOATIME) + return -EINVAL; + } else if (flags & MS_NOATIME) { + mnt_flags |= MNT_NOATIME; + } else { + mnt_flags |= MNT_RELATIME; + } + + f = fdget(fs_fd); + if (!f.file) + return -EBADF; + + ret = -EINVAL; + if (f.file->f_op != &fs_fs_fops) + goto err_fsfd; + + sc = f.file->private_data; + + ret = -EPERM; + if (!may_mount() || + ((sc->ms_flags & MS_MANDLOCK) && !may_mandlock())) + goto err_fsfd; + + /* Prevent further changes. */ + inode = file_inode(f.file); + ret = inode_lock_killable(inode); + if (ret < 0) + goto err_fsfd; + ret = -EBUSY; + if (!sc->mounted) { + sc->mounted = true; + ret = 0; + } + inode_unlock(inode); + if (ret < 0) + goto err_fsfd; + + /* Find the mountpoint. A container can be specified in dfd. */ + lookup_flags = LOOKUP_FOLLOW | LOOKUP_AUTOMOUNT; + if (at_flags & AT_SYMLINK_NOFOLLOW) + lookup_flags &= ~LOOKUP_FOLLOW; + if (at_flags & AT_NO_AUTOMOUNT) + lookup_flags &= ~LOOKUP_AUTOMOUNT; + if (at_flags & AT_EMPTY_PATH) + lookup_flags |= LOOKUP_EMPTY; + ret = user_path_at(dfd, dir_name, lookup_flags, &mountpoint); + if (ret < 0) { + sb_cfg_error(sc, "VFS: Mountpoint lookup failed"); + goto err_fsfd; + } + + ret = security_sb_config_mountpoint(sc, &mountpoint); + if (ret < 0) + goto err_mp; + + ret = do_new_mount_sc(sc, &mountpoint, mnt_flags); + +err_mp: + path_put(&mountpoint); +err_fsfd: + fdput(f); + return ret; +} + +/* * Return true if path is reachable from root * * namespace_sem or mount_lock is held diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index 6238fccaf5a4..e8e473ce5ddd 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -101,6 +101,10 @@ * Equivalent of sb_kern_mount, but with a superblock configuration context. * @sc indicates the superblock configuration context. * @src_sb indicates the new superblock. + * @sb_config_mountpoint: + * Equivalent of sb_mount, but with an sb_config. + * @sc indicates the superblock configuration context. + * @mountpoint indicates the path on which the mount will take place. * * Security hooks for filesystem operations. * @@ -1390,6 +1394,7 @@ union security_list_options { void (*sb_config_free)(struct sb_config *sc); int (*sb_config_parse_option)(struct sb_config *sc, char *opt); int (*sb_config_kern_mount)(struct sb_config *sc, struct super_block *sb); + int (*sb_config_mountpoint)(struct sb_config *sc, struct path *mountpoint); int (*sb_alloc_security)(struct super_block *sb); void (*sb_free_security)(struct super_block *sb); @@ -1704,6 +1709,7 @@ struct security_hook_heads { struct list_head sb_config_free; struct list_head sb_config_parse_option; struct list_head sb_config_kern_mount; + struct list_head sb_config_mountpoint; struct list_head sb_alloc_security; struct list_head sb_free_security; struct list_head sb_copy_data; diff --git a/include/linux/security.h b/include/linux/security.h index 49a7254aa30a..f95dc555cf29 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -226,6 +226,7 @@ int security_sb_config_dup(struct sb_config *sc, struct sb_config *src_sc); void security_sb_config_free(struct sb_config *sc); int security_sb_config_parse_option(struct sb_config *sc, char *opt); int security_sb_config_kern_mount(struct sb_config *sc, struct super_block *sb); +int security_sb_config_mountpoint(struct sb_config *sc, struct path *mountpoint); int security_sb_alloc(struct super_block *sb); void security_sb_free(struct super_block *sb); int security_sb_copy_data(char *orig, char *copy); @@ -541,6 +542,11 @@ static inline int security_sb_config_kern_mount(struct sb_config *sc, { return 0; } +static inline int security_sb_config_mountpoint(struct sb_config *sc, + struct path *mountpoint) +{ + return 0; +} static inline int security_sb_alloc(struct super_block *sb) { diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 91ec8802ad5d..07e4f775f24d 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -906,5 +906,7 @@ asmlinkage long sys_pkey_free(int pkey); asmlinkage long sys_statx(int dfd, const char __user *path, unsigned flags, unsigned mask, struct statx __user *buffer); asmlinkage long sys_fsopen(const char *fs_name, int containerfd, unsigned int flags); +asmlinkage long sys_fsmount(int fsfd, int dfd, const char *path, unsigned int at_flags, + unsigned int flags); #endif diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c index de1dc63e7e47..a0fe764bd5dd 100644 --- a/kernel/sys_ni.c +++ b/kernel/sys_ni.c @@ -261,3 +261,4 @@ cond_syscall(sys_pkey_free); /* fd-based mount */ cond_syscall(sys_fsopen); +cond_syscall(sys_fsmount); diff --git a/security/security.c b/security/security.c index fa9037186634..8b2b7e6b3112 100644 --- a/security/security.c +++ b/security/security.c @@ -334,6 +334,11 @@ int security_sb_config_kern_mount(struct sb_config *sc, struct super_block *sb) return call_int_hook(sb_config_kern_mount, 0, sc, sb); } +int security_sb_config_mountpoint(struct sb_config *sc, struct path *mountpoint) +{ + return call_int_hook(sb_config_mountpoint, 0, sc, mountpoint); +} + int security_sb_alloc(struct super_block *sb) { return call_int_hook(sb_alloc_security, 0, sb); @@ -1691,6 +1696,8 @@ struct security_hook_heads security_hook_heads = { LIST_HEAD_INIT(security_hook_heads.sb_config_parse_option), .sb_config_kern_mount = LIST_HEAD_INIT(security_hook_heads.sb_config_kern_mount), + .sb_config_mountpoint = + LIST_HEAD_INIT(security_hook_heads.sb_config_mountpoint), .sb_alloc_security = LIST_HEAD_INIT(security_hook_heads.sb_alloc_security), .sb_free_security = diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 142be91888c9..e1bf18af72f5 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -2990,6 +2990,18 @@ static int selinux_sb_config_kern_mount(struct sb_config *sc, return rc; } +static int selinux_sb_config_mountpoint(struct sb_config *sc, + struct path *mountpoint) +{ + const struct cred *cred = current_cred(); + int ret; + + ret = path_has_perm(cred, mountpoint, FILE__MOUNTON); + if (ret < 0) + sb_cfg_error(sc, "SELinux: Mount on mountpoint not permitted"); + return ret; +} + /* inode security operations */ static int selinux_inode_alloc_security(struct inode *inode) @@ -6300,6 +6312,7 @@ static struct security_hook_list selinux_hooks[] = { LSM_HOOK_INIT(sb_config_free, selinux_sb_config_free), LSM_HOOK_INIT(sb_config_parse_option, selinux_sb_config_parse_option), LSM_HOOK_INIT(sb_config_kern_mount, selinux_sb_config_kern_mount), + LSM_HOOK_INIT(sb_config_mountpoint, selinux_sb_config_mountpoint), LSM_HOOK_INIT(sb_alloc_security, selinux_sb_alloc_security), LSM_HOOK_INIT(sb_free_security, selinux_sb_free_security),