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, int fh_flags) 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 support decoding of 28 * the file handle if decodeable file handle was requested. 29 */ 30 if (!exportfs_can_encode_fh(path->dentry->d_sb->s_export_op, fh_flags)) 31 return -EOPNOTSUPP; 32 33 if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) 34 return -EFAULT; 35 36 if (f_handle.handle_bytes > MAX_HANDLE_SZ) 37 return -EINVAL; 38 39 handle = kzalloc(struct_size(handle, f_handle, f_handle.handle_bytes), 40 GFP_KERNEL); 41 if (!handle) 42 return -ENOMEM; 43 44 /* convert handle size to multiple of sizeof(u32) */ 45 handle_dwords = f_handle.handle_bytes >> 2; 46 47 /* we ask for a non connectable maybe decodeable file handle */ 48 retval = exportfs_encode_fh(path->dentry, 49 (struct fid *)handle->f_handle, 50 &handle_dwords, fh_flags); 51 handle->handle_type = retval; 52 /* convert handle size to bytes */ 53 handle_bytes = handle_dwords * sizeof(u32); 54 handle->handle_bytes = handle_bytes; 55 if ((handle->handle_bytes > f_handle.handle_bytes) || 56 (retval == FILEID_INVALID) || (retval < 0)) { 57 /* As per old exportfs_encode_fh documentation 58 * we could return ENOSPC to indicate overflow 59 * But file system returned 255 always. So handle 60 * both the values 61 */ 62 if (retval == FILEID_INVALID || retval == -ENOSPC) 63 retval = -EOVERFLOW; 64 /* 65 * set the handle size to zero so we copy only 66 * non variable part of the file_handle 67 */ 68 handle_bytes = 0; 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 struct_size(handle, f_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 * and whether a decodable file handle is required. 88 * 89 * @handle->handle_size indicate the space available to store the 90 * variable part of the file handle in bytes. If there is not 91 * enough space, the field is updated to return the minimum 92 * value required. 93 */ 94 SYSCALL_DEFINE5(name_to_handle_at, int, dfd, const char __user *, name, 95 struct file_handle __user *, handle, int __user *, mnt_id, 96 int, flag) 97 { 98 struct path path; 99 int lookup_flags; 100 int fh_flags; 101 int err; 102 103 if (flag & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH | AT_HANDLE_FID)) 104 return -EINVAL; 105 106 lookup_flags = (flag & AT_SYMLINK_FOLLOW) ? LOOKUP_FOLLOW : 0; 107 fh_flags = (flag & AT_HANDLE_FID) ? EXPORT_FH_FID : 0; 108 if (flag & AT_EMPTY_PATH) 109 lookup_flags |= LOOKUP_EMPTY; 110 err = user_path_at(dfd, name, lookup_flags, &path); 111 if (!err) { 112 err = do_sys_name_to_handle(&path, handle, mnt_id, fh_flags); 113 path_put(&path); 114 } 115 return err; 116 } 117 118 static struct vfsmount *get_vfsmount_from_fd(int fd) 119 { 120 struct vfsmount *mnt; 121 122 if (fd == AT_FDCWD) { 123 struct fs_struct *fs = current->fs; 124 spin_lock(&fs->lock); 125 mnt = mntget(fs->pwd.mnt); 126 spin_unlock(&fs->lock); 127 } else { 128 struct fd f = fdget(fd); 129 if (!f.file) 130 return ERR_PTR(-EBADF); 131 mnt = mntget(f.file->f_path.mnt); 132 fdput(f); 133 } 134 return mnt; 135 } 136 137 static int vfs_dentry_acceptable(void *context, struct dentry *dentry) 138 { 139 return 1; 140 } 141 142 static int do_handle_to_path(int mountdirfd, struct file_handle *handle, 143 struct path *path) 144 { 145 int retval = 0; 146 int handle_dwords; 147 148 path->mnt = get_vfsmount_from_fd(mountdirfd); 149 if (IS_ERR(path->mnt)) { 150 retval = PTR_ERR(path->mnt); 151 goto out_err; 152 } 153 /* change the handle size to multiple of sizeof(u32) */ 154 handle_dwords = handle->handle_bytes >> 2; 155 path->dentry = exportfs_decode_fh(path->mnt, 156 (struct fid *)handle->f_handle, 157 handle_dwords, handle->handle_type, 158 vfs_dentry_acceptable, NULL); 159 if (IS_ERR(path->dentry)) { 160 retval = PTR_ERR(path->dentry); 161 goto out_mnt; 162 } 163 return 0; 164 out_mnt: 165 mntput(path->mnt); 166 out_err: 167 return retval; 168 } 169 170 static int handle_to_path(int mountdirfd, struct file_handle __user *ufh, 171 struct path *path) 172 { 173 int retval = 0; 174 struct file_handle f_handle; 175 struct file_handle *handle = NULL; 176 177 /* 178 * With handle we don't look at the execute bit on the 179 * directory. Ideally we would like CAP_DAC_SEARCH. 180 * But we don't have that 181 */ 182 if (!capable(CAP_DAC_READ_SEARCH)) { 183 retval = -EPERM; 184 goto out_err; 185 } 186 if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) { 187 retval = -EFAULT; 188 goto out_err; 189 } 190 if ((f_handle.handle_bytes > MAX_HANDLE_SZ) || 191 (f_handle.handle_bytes == 0)) { 192 retval = -EINVAL; 193 goto out_err; 194 } 195 handle = kmalloc(struct_size(handle, f_handle, f_handle.handle_bytes), 196 GFP_KERNEL); 197 if (!handle) { 198 retval = -ENOMEM; 199 goto out_err; 200 } 201 /* copy the full handle */ 202 *handle = f_handle; 203 if (copy_from_user(&handle->f_handle, 204 &ufh->f_handle, 205 f_handle.handle_bytes)) { 206 retval = -EFAULT; 207 goto out_handle; 208 } 209 210 retval = do_handle_to_path(mountdirfd, handle, path); 211 212 out_handle: 213 kfree(handle); 214 out_err: 215 return retval; 216 } 217 218 static long do_handle_open(int mountdirfd, struct file_handle __user *ufh, 219 int open_flag) 220 { 221 long retval = 0; 222 struct path path; 223 struct file *file; 224 int fd; 225 226 retval = handle_to_path(mountdirfd, ufh, &path); 227 if (retval) 228 return retval; 229 230 fd = get_unused_fd_flags(open_flag); 231 if (fd < 0) { 232 path_put(&path); 233 return fd; 234 } 235 file = file_open_root(&path, "", open_flag, 0); 236 if (IS_ERR(file)) { 237 put_unused_fd(fd); 238 retval = PTR_ERR(file); 239 } else { 240 retval = fd; 241 fd_install(fd, file); 242 } 243 path_put(&path); 244 return retval; 245 } 246 247 /** 248 * sys_open_by_handle_at: Open the file handle 249 * @mountdirfd: directory file descriptor 250 * @handle: file handle to be opened 251 * @flags: open flags. 252 * 253 * @mountdirfd indicate the directory file descriptor 254 * of the mount point. file handle is decoded relative 255 * to the vfsmount pointed by the @mountdirfd. @flags 256 * value is same as the open(2) flags. 257 */ 258 SYSCALL_DEFINE3(open_by_handle_at, int, mountdirfd, 259 struct file_handle __user *, handle, 260 int, flags) 261 { 262 long ret; 263 264 if (force_o_largefile()) 265 flags |= O_LARGEFILE; 266 267 ret = do_handle_open(mountdirfd, handle, flags); 268 return ret; 269 } 270 271 #ifdef CONFIG_COMPAT 272 /* 273 * Exactly like fs/open.c:sys_open_by_handle_at(), except that it 274 * doesn't set the O_LARGEFILE flag. 275 */ 276 COMPAT_SYSCALL_DEFINE3(open_by_handle_at, int, mountdirfd, 277 struct file_handle __user *, handle, int, flags) 278 { 279 return do_handle_open(mountdirfd, handle, flags); 280 } 281 #endif 282