crosvm/fuzz/qcow_fuzzer.rs
Daniel Verkamp eb1640e301 disk: limit maximum nesting depth
Impose a limit on the maximum nesting of file formats that can open more
files. For example, a qcow2 file can have a backing file, which could be
another qcow2 file with a backing file (or even the same file as the
original), potentially causing unbounded recursion.

BUG=b:198326611
TEST=cros_fuzz

Change-Id: I2f8573a7c71c6d8b310f2c2a75a240f2f8f0c9b1
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3146214
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Cody Schuffelen <schuffelen@google.com>
Reviewed-by: Chirantan Ekbote <chirantan@chromium.org>
Commit-Queue: Daniel Verkamp <dverkamp@chromium.org>
2021-09-17 02:55:04 +00:00

39 lines
1.2 KiB
Rust

// 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]
use cros_fuzz::fuzz_target;
use disk::QcowFile;
use tempfile;
use std::io::{Cursor, Read, Seek, SeekFrom, Write};
use std::mem::size_of;
// 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.
fuzz_target!(|bytes| {
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 max_nesting_depth = 10;
let mut disk_file = tempfile::tempfile().unwrap();
disk_file.write_all(&bytes[16..]).unwrap();
disk_file.seek(SeekFrom::Start(0)).unwrap();
if let Ok(mut qcow) = QcowFile::from(disk_file, max_nesting_depth) {
if qcow.seek(SeekFrom::Start(addr)).is_ok() {
let _ = qcow.write_all(&value.to_le_bytes());
}
}
});
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)
}