1 #include <linux/syscalls.h> 2 #include <linux/slab.h> 3 #include <linux/fs.h> 4 #include <linux/file.h> 5 #include <linux/mount.h> 6 #include <linux/namei.h> 7 #include <linux/exportfs.h> 8 #include <linux/fs_struct.h> 9 #include <linux/fsnotify.h> 10 #include <asm/uaccess.h> 11 #include "internal.h" 12 13 static long do_sys_name_to_handle(struct path *path, 14 struct file_handle __user *ufh, 15 int __user *mnt_id) 16 { 17 long retval; 18 struct file_handle f_handle; 19 int handle_dwords, handle_bytes; 20 struct file_handle *handle = NULL; 21 22 /* 23 * We need t make sure wether the file system 24 * support decoding of the file handle 25 */ 26 if (!path->mnt->mnt_sb->s_export_op || 27 !path->mnt->mnt_sb->s_export_op->fh_to_dentry) 28 return -EOPNOTSUPP; 29 30 if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) 31 return -EFAULT; 32 33 if (f_handle.handle_bytes > MAX_HANDLE_SZ) 34 return -EINVAL; 35 36 handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes, 37 GFP_KERNEL); 38 if (!handle) 39 return -ENOMEM; 40 41 /* convert handle size to multiple of sizeof(u32) */ 42 handle_dwords = f_handle.handle_bytes >> 2; 43 44 /* we ask for a non connected handle */ 45 retval = exportfs_encode_fh(path->dentry, 46 (struct fid *)handle->f_handle, 47 &handle_dwords, 0); 48 handle->handle_type = retval; 49 /* convert handle size to bytes */ 50 handle_bytes = handle_dwords * sizeof(u32); 51 handle->handle_bytes = handle_bytes; 52 if ((handle->handle_bytes > f_handle.handle_bytes) || 53 (retval == 255) || (retval == -ENOSPC)) { 54 /* As per old exportfs_encode_fh documentation 55 * we could return ENOSPC to indicate overflow 56 * But file system returned 255 always. So handle 57 * both the values 58 */ 59 /* 60 * set the handle size to zero so we copy only 61 * non variable part of the file_handle 62 */ 63 handle_bytes = 0; 64 retval = -EOVERFLOW; 65 } else 66 retval = 0; 67 /* copy the mount id */ 68 if (copy_to_user(mnt_id, &path->mnt->mnt_id, sizeof(*mnt_id)) || 69 copy_to_user(ufh, handle, 70 sizeof(struct file_handle) + handle_bytes)) 71 retval = -EFAULT; 72 kfree(handle); 73 return retval; 74 } 75 76 /** 77 * sys_name_to_handle_at: convert name to handle 78 * @dfd: directory relative to which name is interpreted if not absolute 79 * @name: name that should be converted to handle. 80 * @handle: resulting file handle 81 * @mnt_id: mount id of the file system containing the file 82 * @flag: flag value to indicate whether to follow symlink or not 83 * 84 * @handle->handle_size indicate the space available to store the 85 * variable part of the file handle in bytes. If there is not 86 * enough space, the field is updated to return the minimum 87 * value required. 88 */ 89 SYSCALL_DEFINE5(name_to_handle_at, int, dfd, const char __user *, name, 90 struct file_handle __user *, handle, int __user *, mnt_id, 91 int, flag) 92 { 93 struct path path; 94 int lookup_flags; 95 int err; 96 97 if ((flag & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0) 98 return -EINVAL; 99 100 lookup_flags = (flag & AT_SYMLINK_FOLLOW) ? LOOKUP_FOLLOW : 0; 101 if (flag & AT_EMPTY_PATH) 102 lookup_flags |= LOOKUP_EMPTY; 103 err = user_path_at(dfd, name, lookup_flags, &path); 104 if (!err) { 105 err = do_sys_name_to_handle(&path, handle, mnt_id); 106 path_put(&path); 107 } 108 return err; 109 } 110 111 static struct vfsmount *get_vfsmount_from_fd(int fd) 112 { 113 struct path path; 114 115 if (fd == AT_FDCWD) { 116 struct fs_struct *fs = current->fs; 117 spin_lock(&fs->lock); 118 path = fs->pwd; 119 mntget(path.mnt); 120 spin_unlock(&fs->lock); 121 } else { 122 int fput_needed; 123 struct file *file = fget_light(fd, &fput_needed); 124 if (!file) 125 return ERR_PTR(-EBADF); 126 path = file->f_path; 127 mntget(path.mnt); 128 fput_light(file, fput_needed); 129 } 130 return path.mnt; 131 } 132 133 static int vfs_dentry_acceptable(void *context, struct dentry *dentry) 134 { 135 return 1; 136 } 137 138 static int do_handle_to_path(int mountdirfd, struct file_handle *handle, 139 struct path *path) 140 { 141 int retval = 0; 142 int handle_dwords; 143 144 path->mnt = get_vfsmount_from_fd(mountdirfd); 145 if (IS_ERR(path->mnt)) { 146 retval = PTR_ERR(path->mnt); 147 goto out_err; 148 } 149 /* change the handle size to multiple of sizeof(u32) */ 150 handle_dwords = handle->handle_bytes >> 2; 151 path->dentry = exportfs_decode_fh(path->mnt, 152 (struct fid *)handle->f_handle, 153 handle_dwords, handle->handle_type, 154 vfs_dentry_acceptable, NULL); 155 if (IS_ERR(path->dentry)) { 156 retval = PTR_ERR(path->dentry); 157 goto out_mnt; 158 } 159 return 0; 160 out_mnt: 161 mntput(path->mnt); 162 out_err: 163 return retval; 164 } 165 166 static int handle_to_path(int mountdirfd, struct file_handle __user *ufh, 167 struct path *path) 168 { 169 int retval = 0; 170 struct file_handle f_handle; 171 struct file_handle *handle = NULL; 172 173 /* 174 * With handle we don't look at the execute bit on the 175 * the directory. Ideally we would like CAP_DAC_SEARCH. 176 * But we don't have that 177 */ 178 if (!capable(CAP_DAC_READ_SEARCH)) { 179 retval = -EPERM; 180 goto out_err; 181 } 182 if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) { 183 retval = -EFAULT; 184 goto out_err; 185 } 186 if ((f_handle.handle_bytes > MAX_HANDLE_SZ) || 187 (f_handle.handle_bytes == 0)) { 188 retval = -EINVAL; 189 goto out_err; 190 } 191 handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes, 192 GFP_KERNEL); 193 if (!handle) { 194 retval = -ENOMEM; 195 goto out_err; 196 } 197 /* copy the full handle */ 198 if (copy_from_user(handle, ufh, 199 sizeof(struct file_handle) + 200 f_handle.handle_bytes)) { 201 retval = -EFAULT; 202 goto out_handle; 203 } 204 205 retval = do_handle_to_path(mountdirfd, handle, path); 206 207 out_handle: 208 kfree(handle); 209 out_err: 210 return retval; 211 } 212 213 long do_handle_open(int mountdirfd, 214 struct file_handle __user *ufh, int open_flag) 215 { 216 long retval = 0; 217 struct path path; 218 struct file *file; 219 int fd; 220 221 retval = handle_to_path(mountdirfd, ufh, &path); 222 if (retval) 223 return retval; 224 225 fd = get_unused_fd_flags(open_flag); 226 if (fd < 0) { 227 path_put(&path); 228 return fd; 229 } 230 file = file_open_root(path.dentry, path.mnt, "", open_flag); 231 if (IS_ERR(file)) { 232 put_unused_fd(fd); 233 retval = PTR_ERR(file); 234 } else { 235 retval = fd; 236 fsnotify_open(file); 237 fd_install(fd, file); 238 } 239 path_put(&path); 240 return retval; 241 } 242 243 /** 244 * sys_open_by_handle_at: Open the file handle 245 * @mountdirfd: directory file descriptor 246 * @handle: file handle to be opened 247 * @flag: open flags. 248 * 249 * @mountdirfd indicate the directory file descriptor 250 * of the mount point. file handle is decoded relative 251 * to the vfsmount pointed by the @mountdirfd. @flags 252 * value is same as the open(2) flags. 253 */ 254 SYSCALL_DEFINE3(open_by_handle_at, int, mountdirfd, 255 struct file_handle __user *, handle, 256 int, flags) 257 { 258 long ret; 259 260 if (force_o_largefile()) 261 flags |= O_LARGEFILE; 262 263 ret = do_handle_open(mountdirfd, handle, flags); 264 return ret; 265 } 266