1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/syscalls.h>
3 #include <linux/slab.h>
5 #include <linux/file.h>
6 #include <linux/mount.h>
7 #include <linux/namei.h>
8 #include <linux/exportfs.h>
9 #include <linux/fs_struct.h>
10 #include <linux/fsnotify.h>
11 #include <linux/personality.h>
12 #include <linux/uaccess.h>
13 #include <linux/compat.h>
17 static long do_sys_name_to_handle(const struct path *path,
18 struct file_handle __user *ufh,
19 int __user *mnt_id, int fh_flags)
22 struct file_handle f_handle;
23 int handle_dwords, handle_bytes;
24 struct file_handle *handle = NULL;
27 * We need to make sure whether the file system support decoding of
28 * the file handle if decodeable file handle was requested.
29 * Otherwise, even empty export_operations are sufficient to opt-in
32 if (!path->dentry->d_sb->s_export_op ||
33 (!(fh_flags & EXPORT_FH_FID) &&
34 !path->dentry->d_sb->s_export_op->fh_to_dentry))
37 if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle)))
40 if (f_handle.handle_bytes > MAX_HANDLE_SZ)
43 handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes,
48 /* convert handle size to multiple of sizeof(u32) */
49 handle_dwords = f_handle.handle_bytes >> 2;
51 /* we ask for a non connectable maybe decodeable file handle */
52 retval = exportfs_encode_fh(path->dentry,
53 (struct fid *)handle->f_handle,
54 &handle_dwords, fh_flags);
55 handle->handle_type = retval;
56 /* convert handle size to bytes */
57 handle_bytes = handle_dwords * sizeof(u32);
58 handle->handle_bytes = handle_bytes;
59 if ((handle->handle_bytes > f_handle.handle_bytes) ||
60 (retval == FILEID_INVALID) || (retval < 0)) {
61 /* As per old exportfs_encode_fh documentation
62 * we could return ENOSPC to indicate overflow
63 * But file system returned 255 always. So handle
66 if (retval == FILEID_INVALID || retval == -ENOSPC)
69 * set the handle size to zero so we copy only
70 * non variable part of the file_handle
75 /* copy the mount id */
76 if (put_user(real_mount(path->mnt)->mnt_id, mnt_id) ||
77 copy_to_user(ufh, handle,
78 sizeof(struct file_handle) + handle_bytes))
85 * sys_name_to_handle_at: convert name to handle
86 * @dfd: directory relative to which name is interpreted if not absolute
87 * @name: name that should be converted to handle.
88 * @handle: resulting file handle
89 * @mnt_id: mount id of the file system containing the file
90 * @flag: flag value to indicate whether to follow symlink or not
91 * and whether a decodable file handle is required.
93 * @handle->handle_size indicate the space available to store the
94 * variable part of the file handle in bytes. If there is not
95 * enough space, the field is updated to return the minimum
98 SYSCALL_DEFINE5(name_to_handle_at, int, dfd, const char __user *, name,
99 struct file_handle __user *, handle, int __user *, mnt_id,
107 if (flag & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH | AT_HANDLE_FID))
110 lookup_flags = (flag & AT_SYMLINK_FOLLOW) ? LOOKUP_FOLLOW : 0;
111 fh_flags = (flag & AT_HANDLE_FID) ? EXPORT_FH_FID : 0;
112 if (flag & AT_EMPTY_PATH)
113 lookup_flags |= LOOKUP_EMPTY;
114 err = user_path_at(dfd, name, lookup_flags, &path);
116 err = do_sys_name_to_handle(&path, handle, mnt_id, fh_flags);
122 static struct vfsmount *get_vfsmount_from_fd(int fd)
124 struct vfsmount *mnt;
126 if (fd == AT_FDCWD) {
127 struct fs_struct *fs = current->fs;
128 spin_lock(&fs->lock);
129 mnt = mntget(fs->pwd.mnt);
130 spin_unlock(&fs->lock);
132 struct fd f = fdget(fd);
134 return ERR_PTR(-EBADF);
135 mnt = mntget(f.file->f_path.mnt);
141 static int vfs_dentry_acceptable(void *context, struct dentry *dentry)
146 static int do_handle_to_path(int mountdirfd, struct file_handle *handle,
152 path->mnt = get_vfsmount_from_fd(mountdirfd);
153 if (IS_ERR(path->mnt)) {
154 retval = PTR_ERR(path->mnt);
157 /* change the handle size to multiple of sizeof(u32) */
158 handle_dwords = handle->handle_bytes >> 2;
159 path->dentry = exportfs_decode_fh(path->mnt,
160 (struct fid *)handle->f_handle,
161 handle_dwords, handle->handle_type,
162 vfs_dentry_acceptable, NULL);
163 if (IS_ERR(path->dentry)) {
164 retval = PTR_ERR(path->dentry);
174 static int handle_to_path(int mountdirfd, struct file_handle __user *ufh,
178 struct file_handle f_handle;
179 struct file_handle *handle = NULL;
182 * With handle we don't look at the execute bit on the
183 * directory. Ideally we would like CAP_DAC_SEARCH.
184 * But we don't have that
186 if (!capable(CAP_DAC_READ_SEARCH)) {
190 if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) {
194 if ((f_handle.handle_bytes > MAX_HANDLE_SZ) ||
195 (f_handle.handle_bytes == 0)) {
199 handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes,
205 /* copy the full handle */
207 if (copy_from_user(&handle->f_handle,
209 f_handle.handle_bytes)) {
214 retval = do_handle_to_path(mountdirfd, handle, path);
222 static long do_handle_open(int mountdirfd, struct file_handle __user *ufh,
230 retval = handle_to_path(mountdirfd, ufh, &path);
234 fd = get_unused_fd_flags(open_flag);
239 file = file_open_root(&path, "", open_flag, 0);
242 retval = PTR_ERR(file);
246 fd_install(fd, file);
253 * sys_open_by_handle_at: Open the file handle
254 * @mountdirfd: directory file descriptor
255 * @handle: file handle to be opened
256 * @flags: open flags.
258 * @mountdirfd indicate the directory file descriptor
259 * of the mount point. file handle is decoded relative
260 * to the vfsmount pointed by the @mountdirfd. @flags
261 * value is same as the open(2) flags.
263 SYSCALL_DEFINE3(open_by_handle_at, int, mountdirfd,
264 struct file_handle __user *, handle,
269 if (force_o_largefile())
270 flags |= O_LARGEFILE;
272 ret = do_handle_open(mountdirfd, handle, flags);
278 * Exactly like fs/open.c:sys_open_by_handle_at(), except that it
279 * doesn't set the O_LARGEFILE flag.
281 COMPAT_SYSCALL_DEFINE3(open_by_handle_at, int, mountdirfd,
282 struct file_handle __user *, handle, int, flags)
284 return do_handle_open(mountdirfd, handle, flags);