fuzz: Add qcow fuzzing

Fuzz using the data as a qcow image with an offset and value to write to
the image.

Change-Id: Iff8f2971ba716c93d978e33338ad62b5d487c115
Signed-off-by: Dylan Reid <dgreid@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/871132
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Chirantan Ekbote <chirantan@chromium.org>

fuzz/Cargo.toml

@@ -4,14 +4,20 @@ version = "0.0.1"
 authors = ["The Chromium OS Authors"]
 
 [dependencies]
+devices = { path = "../devices" }
 libc = "*"
 kernel_loader = { path = "../kernel_loader" }
+qcow = { path = "../qcow" }
 sys_util = { path = "../sys_util" }
 
 # Prevent this from interfering with workspaces
 [workspace]
 members = ["."]
 
+[[bin]]
+name = "crosvm_qcow_fuzzer"
+path = "qcow_fuzzer.rs"
+
 [[bin]]
 name = "crosvm_zimage_fuzzer"
 path = "zimage_fuzzer.rs"

fuzz/qcow_fuzzer.rs

@@ -0,0 +1,57 @@
+// Copyright 2019 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#![no_main]
+extern crate libc;
+extern crate qcow;
+extern crate sys_util;
+
+use qcow::QcowFile;
+use sys_util::SharedMemory;
+
+use std::fs::File;
+use std::io::{Cursor, Read, Seek, SeekFrom, Write};
+use std::mem::size_of;
+use std::panic;
+use std::process;
+use std::slice;
+
+// Take the first 64 bits of data as an address and the next 64 bits as data to
+// store there. The rest of the data is used as a qcow image.
+#[export_name = "LLVMFuzzerTestOneInput"]
+pub fn test_one_input(data: *const u8, size: usize) -> i32 {
+    // We cannot unwind past ffi boundaries.
+    panic::catch_unwind(|| {
+        // Safe because the libfuzzer runtime will guarantee that `data` is at least
+        // `size` bytes long and that it will be valid for the lifetime of this
+        // function.
+        let bytes = unsafe { slice::from_raw_parts(data, size) };
+        if bytes.len() < 16 {
+            // Need an address and data, each are 8 bytes.
+            return;
+        }
+        let mut disk_image = Cursor::new(bytes);
+        let addr = read_u64(&mut disk_image);
+        let value = read_u64(&mut disk_image);
+        let shm = SharedMemory::new(None).unwrap();
+        let mut disk_file: File = shm.into();
+        disk_file.write_all(&bytes[16..]).unwrap();
+        disk_file.seek(SeekFrom::Start(0)).unwrap();
+        if let Ok(mut qcow) = QcowFile::from(disk_file) {
+            if qcow.seek(SeekFrom::Start(addr)).is_ok() {
+                let _ = qcow.write_all(&value.to_le_bytes());
+            }
+        }
+    })
+    .err()
+    .map(|_| process::abort());
+
+    0
+}
+
+fn read_u64<T: Read>(readable: &mut T) -> u64 {
+    let mut buf = [0u8; size_of::<u64>()];
+    readable.read_exact(&mut buf[..]).unwrap();
+    u64::from_le_bytes(buf)
+}