vhost_user_block: Only support raw files

This daemon is only a testing tool used during integration testing. The
previous code auto-detected the image type from the file's magic bytes
and opened qcow2 images via QcowFile. Such behaviour has been the cause
of security issues in the past.

Drop the qcow2 detection and open path so only raw images are handled.

Signed-off-by: Rob Bradford <rbradford@meta.com>

vhost_user_block/src/lib.rs

@@ -9,8 +9,8 @@
 // SPDX-License-Identifier: (Apache-2.0 AND BSD-3-Clause)
 
 use std::fs::{File, OpenOptions};
-use std::io::{Read, Seek, SeekFrom, Write};
-use std::ops::{Deref, DerefMut};
+use std::io::{Seek, SeekFrom};
+use std::ops::Deref;
 use std::os::unix::fs::OpenOptionsExt;
 use std::os::unix::io::{FromRawFd, IntoRawFd};
 use std::path::PathBuf;
@@ -19,7 +19,7 @@ use std::sync::{Arc, Mutex, RwLock, RwLockWriteGuard};
 use std::time::Instant;
 use std::{convert, io, process, result};
 
-use block::qcow::{self, ImageType, QcowFile};
+use block::qcow::RawFile;
 use block::{Request, RequestType, VirtioBlockConfig, build_serial};
 use libc::EFD_NONBLOCK;
 use log::{debug, error, info, warn};
@@ -48,9 +48,6 @@ const BLK_SIZE: u32 = 512;
 // and the overhead of the emulation layer.
 const POLL_QUEUE_US: u128 = 50;
 
-trait DiskFile: Read + Seek + Write + Send {}
-impl<D: Read + Seek + Write + Send> DiskFile for D {}
-
 type Result<T> = std::result::Result<T, Error>;
 type VhostUserBackendResult<T> = std::result::Result<T, std::io::Error>;
 
@@ -89,7 +86,7 @@ impl convert::From<Error> for io::Error {
 }
 
 struct VhostUserBlkThread {
-    disk_image: Arc<Mutex<dyn DiskFile>>,
+    disk_image: Arc<Mutex<RawFile>>,
     serial: Vec<u8>,
     disk_nsectors: u64,
     event_idx: bool,
@@ -100,7 +97,7 @@ struct VhostUserBlkThread {
 
 impl VhostUserBlkThread {
     fn new(
-        disk_image: Arc<Mutex<dyn DiskFile>>,
+        disk_image: Arc<Mutex<RawFile>>,
         serial: Vec<u8>,
         disk_nsectors: u64,
         writeback: Arc<AtomicBool>,
@@ -133,7 +130,7 @@ impl VhostUserBlkThread {
                     debug!("element is a valid request");
                     request.writeback = self.writeback.load(Ordering::Acquire);
                     let (status, len) = match request.execute(
-                        &mut self.disk_image.lock().unwrap().deref_mut(),
+                        &mut *self.disk_image.lock().unwrap(),
                         self.disk_nsectors,
                         desc_chain.memory(),
                         &self.serial,
@@ -217,16 +214,10 @@ impl VhostUserBlkBackend {
             options.custom_flags(libc::O_DIRECT);
         }
         let image: File = options.open(image_path).unwrap();
-        let mut raw_img: qcow::RawFile = qcow::RawFile::new(image, direct);
+        let raw_img = RawFile::new(image, direct);
 
         let serial = build_serial(&PathBuf::from(&image_path));
-        let image_type = qcow::detect_image_type(&mut raw_img).unwrap();
-        let image = match image_type {
-            ImageType::Raw => Arc::new(Mutex::new(raw_img)) as Arc<Mutex<dyn DiskFile>>,
-            ImageType::Qcow2 => Arc::new(Mutex::new(
-                QcowFile::from_with_nesting_depth(raw_img, 0, true).unwrap(),
-            )) as Arc<Mutex<dyn DiskFile>>,
-        };
+        let image = Arc::new(Mutex::new(raw_img));
 
         let nsectors = (image.lock().unwrap().seek(SeekFrom::End(0)).unwrap()) / SECTOR_SIZE;
         let config = VirtioBlockConfig {