// SPDX-License-Identifier: GPL-2.0 #include <linux/syscalls.h> #include <linux/slab.h> #include <linux/fs.h> #include <linux/file.h> #include <linux/mount.h> #include <linux/namei.h> #include <linux/exportfs.h> #include <linux/fs_struct.h> #include <linux/fsnotify.h> #include <linux/personality.h> #include <linux/uaccess.h> #include <linux/compat.h> #include "internal.h" #include "mount.h" static long do_sys_name_to_handle(struct path *path, struct file_handle __user *ufh, int __user *mnt_id) { long retval; struct file_handle f_handle; int handle_dwords, handle_bytes; struct file_handle *handle = NULL; /* * We need to make sure whether the file system * support decoding of the file handle */ if (!path->dentry->d_sb->s_export_op || !path->dentry->d_sb->s_export_op->fh_to_dentry) return -EOPNOTSUPP; if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) return -EFAULT; if (f_handle.handle_bytes > MAX_HANDLE_SZ) return -EINVAL; handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes, GFP_KERNEL); if (!handle) return -ENOMEM; /* convert handle size to multiple of sizeof(u32) */ handle_dwords = f_handle.handle_bytes >> 2; /* we ask for a non connected handle */ retval = exportfs_encode_fh(path->dentry, (struct fid *)handle->f_handle, &handle_dwords, 0); handle->handle_type = retval; /* convert handle size to bytes */ handle_bytes = handle_dwords * sizeof(u32); handle->handle_bytes = handle_bytes; if ((handle->handle_bytes > f_handle.handle_bytes) || (retval == FILEID_INVALID) || (retval == -ENOSPC)) { /* As per old exportfs_encode_fh documentation * we could return ENOSPC to indicate overflow * But file system returned 255 always. So handle * both the values */ /* * set the handle size to zero so we copy only * non variable part of the file_handle */ handle_bytes = 0; retval = -EOVERFLOW; } else retval = 0; /* copy the mount id */ if (put_user(real_mount(path->mnt)->mnt_id, mnt_id) || copy_to_user(ufh, handle, sizeof(struct file_handle) + handle_bytes)) retval = -EFAULT; kfree(handle); return retval; } /** * sys_name_to_handle_at: convert name to handle * @dfd: directory relative to which name is interpreted if not absolute * @name: name that should be converted to handle. * @handle: resulting file handle * @mnt_id: mount id of the file system containing the file * @flag: flag value to indicate whether to follow symlink or not * * @handle->handle_size indicate the space available to store the * variable part of the file handle in bytes. If there is not * enough space, the field is updated to return the minimum * value required. */ SYSCALL_DEFINE5(name_to_handle_at, int, dfd, const char __user *, name, struct file_handle __user *, handle, int __user *, mnt_id, int, flag) { struct path path; int lookup_flags; int err; if ((flag & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0) return -EINVAL; lookup_flags = (flag & AT_SYMLINK_FOLLOW) ? LOOKUP_FOLLOW : 0; if (flag & AT_EMPTY_PATH) lookup_flags |= LOOKUP_EMPTY; err = user_path_at(dfd, name, lookup_flags, &path); if (!err) { err = do_sys_name_to_handle(&path, handle, mnt_id); path_put(&path); } return err; } static struct vfsmount *get_vfsmount_from_fd(int fd) { struct vfsmount *mnt; if (fd == AT_FDCWD) { struct fs_struct *fs = current->fs; spin_lock(&fs->lock); mnt = mntget(fs->pwd.mnt); spin_unlock(&fs->lock); } else { struct fd f = fdget(fd); if (!f.file) return ERR_PTR(-EBADF); mnt = mntget(f.file->f_path.mnt); fdput(f); } return mnt; } static int vfs_dentry_acceptable(void *context, struct dentry *dentry) { return 1; } static int do_handle_to_path(int mountdirfd, struct file_handle *handle, struct path *path) { int retval = 0; int handle_dwords; path->mnt = get_vfsmount_from_fd(mountdirfd); if (IS_ERR(path->mnt)) { retval = PTR_ERR(path->mnt); goto out_err; } /* change the handle size to multiple of sizeof(u32) */ handle_dwords = handle->handle_bytes >> 2; path->dentry = exportfs_decode_fh(path->mnt, (struct fid *)handle->f_handle, handle_dwords, handle->handle_type, vfs_dentry_acceptable, NULL); if (IS_ERR(path->dentry)) { retval = PTR_ERR(path->dentry); goto out_mnt; } return 0; out_mnt: mntput(path->mnt); out_err: return retval; } static int handle_to_path(int mountdirfd, struct file_handle __user *ufh, struct path *path) { int retval = 0; struct file_handle f_handle; struct file_handle *handle = NULL; /* * With handle we don't look at the execute bit on the * the directory. Ideally we would like CAP_DAC_SEARCH. * But we don't have that */ if (!capable(CAP_DAC_READ_SEARCH)) { retval = -EPERM; goto out_err; } if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) { retval = -EFAULT; goto out_err; } if ((f_handle.handle_bytes > MAX_HANDLE_SZ) || (f_handle.handle_bytes == 0)) { retval = -EINVAL; goto out_err; } handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes, GFP_KERNEL); if (!handle) { retval = -ENOMEM; goto out_err; } /* copy the full handle */ *handle = f_handle; if (copy_from_user(&handle->f_handle, &ufh->f_handle, f_handle.handle_bytes)) { retval = -EFAULT; goto out_handle; } retval = do_handle_to_path(mountdirfd, handle, path); out_handle: kfree(handle); out_err: return retval; } static long do_handle_open(int mountdirfd, struct file_handle __user *ufh, int open_flag) { long retval = 0; struct path path; struct file *file; int fd; retval = handle_to_path(mountdirfd, ufh, &path); if (retval) return retval; fd = get_unused_fd_flags(open_flag); if (fd < 0) { path_put(&path); return fd; } file = file_open_root(path.dentry, path.mnt, "", open_flag, 0); if (IS_ERR(file)) { put_unused_fd(fd); retval = PTR_ERR(file); } else { retval = fd; fsnotify_open(file); fd_install(fd, file); } path_put(&path); return retval; } /** * sys_open_by_handle_at: Open the file handle * @mountdirfd: directory file descriptor * @handle: file handle to be opened * @flags: open flags. * * @mountdirfd indicate the directory file descriptor * of the mount point. file handle is decoded relative * to the vfsmount pointed by the @mountdirfd. @flags * value is same as the open(2) flags. */ SYSCALL_DEFINE3(open_by_handle_at, int, mountdirfd, struct file_handle __user *, handle, int, flags) { long ret; if (force_o_largefile()) flags |= O_LARGEFILE; ret = do_handle_open(mountdirfd, handle, flags); return ret; } #ifdef CONFIG_COMPAT /* * Exactly like fs/open.c:sys_open_by_handle_at(), except that it * doesn't set the O_LARGEFILE flag. */ COMPAT_SYSCALL_DEFINE3(open_by_handle_at, int, mountdirfd, struct file_handle __user *, handle, int, flags) { return do_handle_open(mountdirfd, handle, flags); } #endif