eCryptfs: Propagate vfs_read and vfs_write return codes

Errors returned from vfs_read() and vfs_write() calls to the lower
filesystem were being masked as -EINVAL. This caused some confusion to
users who saw EINVAL instead of ENOSPC when the disk was full, for
instance.

Also, the actual bytes read or written were not accessible by callers to
ecryptfs_read_lower() and ecryptfs_write_lower(), which may be useful in
some cases. This patch updates the error handling logic where those
functions are called in order to accept positive return codes indicating
success.

Cc: Eric Sandeen <[e-mail]>
Acked-by: Serge Hallyn <[e-mail]>
Cc: [e-mail]
Signed-off-by: Tyler Hicks <[e-mail]>

fs/ecryptfs/crypto.c

···
 				  + extent_offset), crypt_stat);
 		rc = ecryptfs_write_lower(ecryptfs_inode, enc_extent_virt,
 					  offset, crypt_stat->extent_size);
-		if (rc) {
+		if (rc < 0) {
 			ecryptfs_printk(KERN_ERR, "Error attempting "
 					"to write lower page; rc = [%d]"
 					"\n", rc);
 			goto out;
 		}
 	}
+	rc = 0;
 out:
 	if (enc_extent_page) {
 		kunmap(enc_extent_page);
···
 		rc = ecryptfs_read_lower(enc_extent_virt, offset,
 					 crypt_stat->extent_size,
 					 ecryptfs_inode);
-		if (rc) {
+		if (rc < 0) {
 			ecryptfs_printk(KERN_ERR, "Error attempting "
 					"to read lower page; rc = [%d]"
 					"\n", rc);
···
 		crypt_stat->extent_size = ECRYPTFS_DEFAULT_EXTENT_SIZE;
 	rc = ecryptfs_read_lower(data, 0, crypt_stat->extent_size,
 				 ecryptfs_inode);
-	if (rc) {
+	if (rc < 0) {
 		printk(KERN_ERR "%s: Error reading header region; rc = [%d]\n",
 		       __func__, rc);
 		goto out;
 	}
 	if (!contains_ecryptfs_marker(data + ECRYPTFS_FILE_SIZE_BYTES)) {
 		rc = -EINVAL;
-	}
+	} else
+		rc = 0;
 out:
 	return rc;
 }
···
 
 	rc = ecryptfs_write_lower(ecryptfs_dentry->d_inode, virt,
 				  0, virt_len);
-	if (rc)
+	if (rc < 0)
 		printk(KERN_ERR "%s: Error attempting to write header "
-		       "information to lower file; rc = [%d]\n", __func__,
-		       rc);
+		       "information to lower file; rc = [%d]\n", __func__, rc);
+	else
+		rc = 0;
 	return rc;
 }
 
···
 	}
 	rc = ecryptfs_read_lower(page_virt, 0, crypt_stat->extent_size,
 				 ecryptfs_inode);
-	if (!rc)
+	if (rc >= 0)
 		rc = ecryptfs_read_headers_virt(page_virt, crypt_stat,
 						ecryptfs_dentry,
 						ECRYPTFS_VALIDATE_HEADER_SIZE);

fs/ecryptfs/mmap.c

···
 	rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
 				  sizeof(u64));
 	kfree(file_size_virt);
-	if (rc)
+	if (rc < 0)
 		printk(KERN_ERR "%s: Error writing file size to header; "
 		       "rc = [%d]\n", __func__, rc);
+	else
+		rc = 0;
 out:
 	return rc;
 }

fs/ecryptfs/read_write.c

···
  *
  * Write data to the lower file.
  *
- * Returns zero on success; non-zero on error
+ * Returns bytes written on success; less than zero on error
  */
 int ecryptfs_write_lower(struct inode *ecryptfs_inode, char *data,
 			 loff_t offset, size_t size)
 {
 	struct ecryptfs_inode_info *inode_info;
-	ssize_t octets_written;
 	mm_segment_t fs_save;
-	int rc = 0;
+	ssize_t rc;
 
 	inode_info = ecryptfs_inode_to_private(ecryptfs_inode);
 	mutex_lock(&inode_info->lower_file_mutex);
···
 	inode_info->lower_file->f_pos = offset;
 	fs_save = get_fs();
 	set_fs(get_ds());
-	octets_written = vfs_write(inode_info->lower_file, data, size,
-				   &inode_info->lower_file->f_pos);
+	rc = vfs_write(inode_info->lower_file, data, size,
+		       &inode_info->lower_file->f_pos);
 	set_fs(fs_save);
-	if (octets_written < 0) {
-		printk(KERN_ERR "%s: octets_written = [%td]; "
-		       "expected [%td]\n", __func__, octets_written, size);
-		rc = -EINVAL;
-	}
 	mutex_unlock(&inode_info->lower_file_mutex);
 	mark_inode_dirty_sync(ecryptfs_inode);
 	return rc;
···
 		  + offset_in_page);
 	virt = kmap(page_for_lower);
 	rc = ecryptfs_write_lower(ecryptfs_inode, virt, offset, size);
+	if (rc > 0)
+		rc = 0;
 	kunmap(page_for_lower);
 	return rc;
 }
···
  * Read @size bytes of data at byte offset @offset from the lower
  * inode into memory location @data.
  *
- * Returns zero on success; non-zero on error
+ * Returns bytes read on success; 0 on EOF; less than zero on error
  */
 int ecryptfs_read_lower(char *data, loff_t offset, size_t size,
 			struct inode *ecryptfs_inode)
 {
 	struct ecryptfs_inode_info *inode_info =
 		ecryptfs_inode_to_private(ecryptfs_inode);
-	ssize_t octets_read;
 	mm_segment_t fs_save;
-	int rc = 0;
+	ssize_t rc;
 
 	mutex_lock(&inode_info->lower_file_mutex);
 	BUG_ON(!inode_info->lower_file);
 	inode_info->lower_file->f_pos = offset;
 	fs_save = get_fs();
 	set_fs(get_ds());
-	octets_read = vfs_read(inode_info->lower_file, data, size,
-			       &inode_info->lower_file->f_pos);
+	rc = vfs_read(inode_info->lower_file, data, size,
+		      &inode_info->lower_file->f_pos);
 	set_fs(fs_save);
-	if (octets_read < 0) {
-		printk(KERN_ERR "%s: octets_read = [%td]; "
-		       "expected [%td]\n", __func__, octets_read, size);
-		rc = -EINVAL;
-	}
 	mutex_unlock(&inode_info->lower_file_mutex);
 	return rc;
 }
···
 	offset = ((((loff_t)page_index) << PAGE_CACHE_SHIFT) + offset_in_page);
 	virt = kmap(page_for_ecryptfs);
 	rc = ecryptfs_read_lower(virt, offset, size, ecryptfs_inode);
+	if (rc > 0)
+		rc = 0;
 	kunmap(page_for_ecryptfs);
 	flush_dcache_page(page_for_ecryptfs);
 	return rc;