fuzz: Add new fuzzer for emulated serial device

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

fuzz/fuzz_targets/serial.rs

@@ -0,0 +1,73 @@
+// Copyright © 2022 Intel Corporation
+//
+// SPDX-License-Identifier: Apache-2.0
+
+#![no_main]
+use devices::legacy::Serial;
+use libc::EFD_NONBLOCK;
+use libfuzzer_sys::fuzz_target;
+use std::sync::Arc;
+use vm_device::interrupt::{InterruptIndex, InterruptSourceConfig, InterruptSourceGroup};
+use vm_device::BusDevice;
+use vmm_sys_util::eventfd::EventFd;
+
+fuzz_target!(|bytes| {
+    let mut serial = Serial::new_sink(
+        "serial".into(),
+        Arc::new(TestInterrupt::new(EventFd::new(EFD_NONBLOCK).unwrap())),
+    );
+
+    let mut i = 0;
+    while i < bytes.len() {
+        let choice = bytes.get(i).unwrap_or(&0) % 3;
+        i += 1;
+
+        match choice {
+            0 => {
+                let offset = (bytes.get(i).unwrap_or(&0) % 8) as u64;
+                i += 1;
+                let mut out_bytes = vec![0];
+                serial.read(0, offset, &mut out_bytes);
+            }
+            1 => {
+                let offset = (bytes.get(i).unwrap_or(&0) % 8) as u64;
+                i += 1;
+                let data = vec![*bytes.get(i).unwrap_or(&0)];
+                i += 1;
+                serial.write(0, offset, &data);
+            }
+            _ => {
+                let data = vec![*bytes.get(i).unwrap_or(&0)];
+                i += 1;
+                serial.queue_input_bytes(&data).ok();
+            }
+        }
+    }
+});
+
+struct TestInterrupt {
+    event_fd: EventFd,
+}
+
+impl InterruptSourceGroup for TestInterrupt {
+    fn trigger(&self, _index: InterruptIndex) -> Result<(), std::io::Error> {
+        self.event_fd.write(1)
+    }
+    fn update(
+        &self,
+        _index: InterruptIndex,
+        _config: InterruptSourceConfig,
+        _masked: bool,
+    ) -> Result<(), std::io::Error> {
+        Ok(())
+    }
+    fn notifier(&self, _index: InterruptIndex) -> Option<EventFd> {
+        Some(self.event_fd.try_clone().unwrap())
+    }
+}
+
+impl TestInterrupt {
+    fn new(event_fd: EventFd) -> Self {
+        TestInterrupt { event_fd }
+    }
+}