1 // SPDX-License-Identifier: GPL-2.0 2 #include <linux/syscalls.h> 3 #include <linux/slab.h> 4 #include <linux/fs.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> 14 #include "internal.h" 15 #include "mount.h" 16 17 static long do_sys_name_to_handle(const struct path *path, 18 struct file_handle __user *ufh, 19 int __user *mnt_id) 20 { 21 long retval; 22 struct file_handle f_handle; 23 int handle_dwords, handle_bytes; 24 struct file_handle *handle = NULL; 25 26 /* 27 * We need to make sure whether the file system 28 * support decoding of the file handle 29 */ 30 if (!path->dentry->d_sb->s_export_op || 31 !path->dentry->d_sb->s_export_op->fh_to_dentry) 32 return -EOPNOTSUPP; 33 34 if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) 35 return -EFAULT; 36 37 if (f_handle.handle_bytes > MAX_HANDLE_SZ) 38 return -EINVAL; 39 40 handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes, 41 GFP_KERNEL); 42 if (!handle) 43 return -ENOMEM; 44 45 /* convert handle size to multiple of sizeof(u32) */ 46 handle_dwords = f_handle.handle_bytes >> 2; 47 48 /* we ask for a non connected handle */ 49 retval = exportfs_encode_fh(path->dentry, 50 (struct fid *)handle->f_handle, 51 &handle_dwords, 0); 52 handle->handle_type = retval; 53 /* convert handle size to bytes */ 54 handle_bytes = handle_dwords * sizeof(u32); 55 handle->handle_bytes = handle_bytes; 56 if ((handle->handle_bytes > f_handle.handle_bytes) || 57 (retval == FILEID_INVALID) || (retval == -ENOSPC)) { 58 /* As per old exportfs_encode_fh documentation 59 * we could return ENOSPC to indicate overflow 60 * But file system returned 255 always. So handle 61 * both the values 62 */ 63 /* 64 * set the handle size to zero so we copy only 65 * non variable part of the file_handle 66 */ 67 handle_bytes = 0; 68 retval = -EOVERFLOW; 69 } else 70 retval = 0; 71 /* copy the mount id */ 72 if (put_user(real_mount(path->mnt)->mnt_id, mnt_id) || 73 copy_to_user(ufh, handle, 74 sizeof(struct file_handle) + handle_bytes)) 75 retval = -EFAULT; 76 kfree(handle); 77 return retval; 78 } 79 80 /** 81 * sys_name_to_handle_at: convert name to handle 82 * @dfd: directory relative to which name is interpreted if not absolute 83 * @name: name that should be converted to handle. 84 * @handle: resulting file handle 85 * @mnt_id: mount id of the file system containing the file 86 * @flag: flag value to indicate whether to follow symlink or not 87 * 88 * @handle->handle_size indicate the space available to store the 89 * variable part of the file handle in bytes. If there is not 90 * enough space, the field is updated to return the minimum 91 * value required. 92 */ 93 SYSCALL_DEFINE5(name_to_handle_at, int, dfd, const char __user *, name, 94 struct file_handle __user *, handle, int __user *, mnt_id, 95 int, flag) 96 { 97 struct path path; 98 int lookup_flags; 99 int err; 100 101 if ((flag & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0) 102 return -EINVAL; 103 104 lookup_flags = (flag & AT_SYMLINK_FOLLOW) ? LOOKUP_FOLLOW : 0; 105 if (flag & AT_EMPTY_PATH) 106 lookup_flags |= LOOKUP_EMPTY; 107 err = user_path_at(dfd, name, lookup_flags, &path); 108 if (!err) { 109 err = do_sys_name_to_handle(&path, handle, mnt_id); 110 path_put(&path); 111 } 112 return err; 113 } 114 115 static struct vfsmount *get_vfsmount_from_fd(int fd) 116 { 117 struct vfsmount *mnt; 118 119 if (fd == AT_FDCWD) { 120 struct fs_struct *fs = current->fs; 121 spin_lock(&fs->lock); 122 mnt = mntget(fs->pwd.mnt); 123 spin_unlock(&fs->lock); 124 } else { 125 struct fd f = fdget(fd); 126 if (!f.file) 127 return ERR_PTR(-EBADF); 128 mnt = mntget(f.file->f_path.mnt); 129 fdput(f); 130 } 131 return mnt; 132 } 133 134 static int vfs_dentry_acceptable(void *context, struct dentry *dentry) 135 { 136 return 1; 137 } 138 139 static int do_handle_to_path(int mountdirfd, struct file_handle *handle, 140 struct path *path) 141 { 142 int retval = 0; 143 int handle_dwords; 144 145 path->mnt = get_vfsmount_from_fd(mountdirfd); 146 if (IS_ERR(path->mnt)) { 147 retval = PTR_ERR(path->mnt); 148 goto out_err; 149 } 150 /* change the handle size to multiple of sizeof(u32) */ 151 handle_dwords = handle->handle_bytes >> 2; 152 path->dentry = exportfs_decode_fh(path->mnt, 153 (struct fid *)handle->f_handle, 154 handle_dwords, handle->handle_type, 155 vfs_dentry_acceptable, NULL); 156 if (IS_ERR(path->dentry)) { 157 retval = PTR_ERR(path->dentry); 158 goto out_mnt; 159 } 160 return 0; 161 out_mnt: 162 mntput(path->mnt); 163 out_err: 164 return retval; 165 } 166 167 static int handle_to_path(int mountdirfd, struct file_handle __user *ufh, 168 struct path *path) 169 { 170 int retval = 0; 171 struct file_handle f_handle; 172 struct file_handle *handle = NULL; 173 174 /* 175 * With handle we don't look at the execute bit on the 176 * directory. Ideally we would like CAP_DAC_SEARCH. 177 * But we don't have that 178 */ 179 if (!capable(CAP_DAC_READ_SEARCH)) { 180 retval = -EPERM; 181 goto out_err; 182 } 183 if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) { 184 retval = -EFAULT; 185 goto out_err; 186 } 187 if ((f_handle.handle_bytes > MAX_HANDLE_SZ) || 188 (f_handle.handle_bytes == 0)) { 189 retval = -EINVAL; 190 goto out_err; 191 } 192 handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes, 193 GFP_KERNEL); 194 if (!handle) { 195 retval = -ENOMEM; 196 goto out_err; 197 } 198 /* copy the full handle */ 199 *handle = f_handle; 200 if (copy_from_user(&handle->f_handle, 201 &ufh->f_handle, 202 f_handle.handle_bytes)) { 203 retval = -EFAULT; 204 goto out_handle; 205 } 206 207 retval = do_handle_to_path(mountdirfd, handle, path); 208 209 out_handle: 210 kfree(handle); 211 out_err: 212 return retval; 213 } 214 215 static long do_handle_open(int mountdirfd, struct file_handle __user *ufh, 216 int open_flag) 217 { 218 long retval = 0; 219 struct path path; 220 struct file *file; 221 int fd; 222 223 retval = handle_to_path(mountdirfd, ufh, &path); 224 if (retval) 225 return retval; 226 227 fd = get_unused_fd_flags(open_flag); 228 if (fd < 0) { 229 path_put(&path); 230 return fd; 231 } 232 file = file_open_root(&path, "", open_flag, 0); 233 if (IS_ERR(file)) { 234 put_unused_fd(fd); 235 retval = PTR_ERR(file); 236 } else { 237 retval = fd; 238 fsnotify_open(file); 239 fd_install(fd, file); 240 } 241 path_put(&path); 242 return retval; 243 } 244 245 /** 246 * sys_open_by_handle_at: Open the file handle 247 * @mountdirfd: directory file descriptor 248 * @handle: file handle to be opened 249 * @flags: open flags. 250 * 251 * @mountdirfd indicate the directory file descriptor 252 * of the mount point. file handle is decoded relative 253 * to the vfsmount pointed by the @mountdirfd. @flags 254 * value is same as the open(2) flags. 255 */ 256 SYSCALL_DEFINE3(open_by_handle_at, int, mountdirfd, 257 struct file_handle __user *, handle, 258 int, flags) 259 { 260 long ret; 261 262 if (force_o_largefile()) 263 flags |= O_LARGEFILE; 264 265 ret = do_handle_open(mountdirfd, handle, flags); 266 return ret; 267 } 268 269 #ifdef CONFIG_COMPAT 270 /* 271 * Exactly like fs/open.c:sys_open_by_handle_at(), except that it 272 * doesn't set the O_LARGEFILE flag. 273 */ 274 COMPAT_SYSCALL_DEFINE3(open_by_handle_at, int, mountdirfd, 275 struct file_handle __user *, handle, int, flags) 276 { 277 return do_handle_open(mountdirfd, handle, flags); 278 } 279 #endif 280