diff options
| -rw-r--r-- | arch/x86/entry/syscalls/syscall_32.tbl | 3 | ||||
| -rw-r--r-- | arch/x86/entry/syscalls/syscall_64.tbl | 1 | ||||
| -rw-r--r-- | fs/namespace.c | 146 | ||||
| -rw-r--r-- | include/linux/syscalls.h | 1 | ||||
| -rw-r--r-- | include/uapi/linux/mount.h | 18 |
5 files changed, 165 insertions, 4 deletions
diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl index 786728143205..5b5c9189c507 100644 --- a/arch/x86/entry/syscalls/syscall_32.tbl +++ b/arch/x86/entry/syscalls/syscall_32.tbl @@ -402,7 +402,8 @@ 388 i386 move_mount sys_move_mount __ia32_sys_move_mount 389 i386 fsopen sys_fsopen __ia32_sys_fsopen 390 i386 fsconfig sys_fsconfig __ia32_sys_fsconfig -# don't use numbers 391 through 392, add new calls at the end +391 i386 fsmount sys_fsmount __ia32_sys_fsmount +# don't use number 392, add new calls at the end 393 i386 semget sys_semget __ia32_sys_semget 394 i386 semctl sys_semctl __ia32_compat_sys_semctl 395 i386 shmget sys_shmget __ia32_sys_shmget diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl index 7039a809d37d..984ad594bb2b 100644 --- a/arch/x86/entry/syscalls/syscall_64.tbl +++ b/arch/x86/entry/syscalls/syscall_64.tbl @@ -347,6 +347,7 @@ 336 common move_mount __x64_sys_move_mount 337 common fsopen __x64_sys_fsopen 338 common fsconfig __x64_sys_fsconfig +339 common fsmount __x64_sys_fsmount # don't use numbers 387 through 423, add new calls after the last # 'common' entry 424 common pidfd_send_signal __x64_sys_pidfd_send_signal diff --git a/fs/namespace.c b/fs/namespace.c index 1e72d19fa4f8..3357c3d65475 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -3334,9 +3334,149 @@ SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, } /* - * Move a mount from one place to another. - * In combination with open_tree(OPEN_TREE_CLONE [| AT_RECURSIVE]) it can be - * used to copy a mount subtree. + * Create a kernel mount representation for a new, prepared superblock + * (specified by fs_fd) and attach to an open_tree-like file descriptor. + */ +SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags, + unsigned int, attr_flags) +{ + struct mnt_namespace *ns; + struct fs_context *fc; + struct file *file; + struct path newmount; + struct mount *mnt; + struct fd f; + unsigned int mnt_flags = 0; + long ret; + + if (!may_mount()) + return -EPERM; + + if ((flags & ~(FSMOUNT_CLOEXEC)) != 0) + return -EINVAL; + + if (attr_flags & ~(MOUNT_ATTR_RDONLY | + MOUNT_ATTR_NOSUID | + MOUNT_ATTR_NODEV | + MOUNT_ATTR_NOEXEC | + MOUNT_ATTR__ATIME | + MOUNT_ATTR_NODIRATIME)) + return -EINVAL; + + if (attr_flags & MOUNT_ATTR_RDONLY) + mnt_flags |= MNT_READONLY; + if (attr_flags & MOUNT_ATTR_NOSUID) + mnt_flags |= MNT_NOSUID; + if (attr_flags & MOUNT_ATTR_NODEV) + mnt_flags |= MNT_NODEV; + if (attr_flags & MOUNT_ATTR_NOEXEC) + mnt_flags |= MNT_NOEXEC; + if (attr_flags & MOUNT_ATTR_NODIRATIME) + mnt_flags |= MNT_NODIRATIME; + + switch (attr_flags & MOUNT_ATTR__ATIME) { + case MOUNT_ATTR_STRICTATIME: + break; + case MOUNT_ATTR_NOATIME: + mnt_flags |= MNT_NOATIME; + break; + case MOUNT_ATTR_RELATIME: + mnt_flags |= MNT_RELATIME; + break; + default: + return -EINVAL; + } + + f = fdget(fs_fd); + if (!f.file) + return -EBADF; + + ret = -EINVAL; + if (f.file->f_op != &fscontext_fops) + goto err_fsfd; + + fc = f.file->private_data; + + ret = mutex_lock_interruptible(&fc->uapi_mutex); + if (ret < 0) + goto err_fsfd; + + /* There must be a valid superblock or we can't mount it */ + ret = -EINVAL; + if (!fc->root) + goto err_unlock; + + ret = -EPERM; + if (mount_too_revealing(fc->root->d_sb, &mnt_flags)) { + pr_warn("VFS: Mount too revealing\n"); + goto err_unlock; + } + + ret = -EBUSY; + if (fc->phase != FS_CONTEXT_AWAITING_MOUNT) + goto err_unlock; + + ret = -EPERM; + if ((fc->sb_flags & SB_MANDLOCK) && !may_mandlock()) + goto err_unlock; + + newmount.mnt = vfs_create_mount(fc); + if (IS_ERR(newmount.mnt)) { + ret = PTR_ERR(newmount.mnt); + goto err_unlock; + } + newmount.dentry = dget(fc->root); + newmount.mnt->mnt_flags = mnt_flags; + + /* We've done the mount bit - now move the file context into more or + * less the same state as if we'd done an fspick(). We don't want to + * do any memory allocation or anything like that at this point as we + * don't want to have to handle any errors incurred. + */ + vfs_clean_context(fc); + + ns = alloc_mnt_ns(current->nsproxy->mnt_ns->user_ns, true); + if (IS_ERR(ns)) { + ret = PTR_ERR(ns); + goto err_path; + } + mnt = real_mount(newmount.mnt); + mnt->mnt_ns = ns; + ns->root = mnt; + ns->mounts = 1; + list_add(&mnt->mnt_list, &ns->list); + + /* Attach to an apparent O_PATH fd with a note that we need to unmount + * it, not just simply put it. + */ + file = dentry_open(&newmount, O_PATH, fc->cred); + if (IS_ERR(file)) { + dissolve_on_fput(newmount.mnt); + ret = PTR_ERR(file); + goto err_path; + } + file->f_mode |= FMODE_NEED_UNMOUNT; + + ret = get_unused_fd_flags((flags & FSMOUNT_CLOEXEC) ? O_CLOEXEC : 0); + if (ret >= 0) + fd_install(ret, file); + else + fput(file); + +err_path: + path_put(&newmount); +err_unlock: + mutex_unlock(&fc->uapi_mutex); +err_fsfd: + fdput(f); + return ret; +} + +/* + * Move a mount from one place to another. In combination with + * fsopen()/fsmount() this is used to install a new mount and in combination + * with open_tree(OPEN_TREE_CLONE [| AT_RECURSIVE]) it can be used to copy + * a mount subtree. * * Note the flags value is a combination of MOVE_MOUNT_* flags. */ diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 925f9dfc356b..0e697f595278 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -992,6 +992,7 @@ asmlinkage long sys_move_mount(int from_dfd, const char __user *from_path, asmlinkage long sys_fsopen(const char __user *fs_name, unsigned int flags); asmlinkage long sys_fsconfig(int fs_fd, unsigned int cmd, const char __user *key, const void __user *value, int aux); +asmlinkage long sys_fsmount(int fs_fd, unsigned int flags, unsigned int ms_flags); asmlinkage long sys_pidfd_send_signal(int pidfd, int sig, siginfo_t __user *info, unsigned int flags); diff --git a/include/uapi/linux/mount.h b/include/uapi/linux/mount.h index 4b90ba9d1770..3888d3b91dc5 100644 --- a/include/uapi/linux/mount.h +++ b/include/uapi/linux/mount.h @@ -91,4 +91,22 @@ enum fsconfig_command { FSCONFIG_CMD_RECONFIGURE = 7, /* Invoke superblock reconfiguration */ }; +/* + * fsmount() flags. + */ +#define FSMOUNT_CLOEXEC 0x00000001 + +/* + * Mount attributes. + */ +#define MOUNT_ATTR_RDONLY 0x00000001 /* Mount read-only */ +#define MOUNT_ATTR_NOSUID 0x00000002 /* Ignore suid and sgid bits */ +#define MOUNT_ATTR_NODEV 0x00000004 /* Disallow access to device special files */ +#define MOUNT_ATTR_NOEXEC 0x00000008 /* Disallow program execution */ +#define MOUNT_ATTR__ATIME 0x00000070 /* Setting on how atime should be updated */ +#define MOUNT_ATTR_RELATIME 0x00000000 /* - Update atime relative to mtime/ctime. */ +#define MOUNT_ATTR_NOATIME 0x00000010 /* - Do not update access times. */ +#define MOUNT_ATTR_STRICTATIME 0x00000020 /* - Always perform atime updates */ +#define MOUNT_ATTR_NODIRATIME 0x00000080 /* Do not update directory access times */ + #endif /* _UAPI_LINUX_MOUNT_H */ |