virtio-devices: console: Skip device-readable descriptors in input queue

The input queue handler wrote data to every descriptor without
checking the write-only flag. The device must not write to
device-readable buffers. Skip them with a warning.

Signed-off-by: Rob Bradford <rbradford@meta.com>
Assisted-by: Claude:claude-opus-4-6

virtio-devices/src/console.rs

@@ -12,7 +12,7 @@ use std::{cmp, io, result};
 use anyhow::anyhow;
 use event_monitor::event;
 use libc::{EFD_NONBLOCK, TIOCGWINSZ};
-use log::{error, info};
+use log::{error, info, warn};
 use seccompiler::SeccompAction;
 use serde::{Deserialize, Serialize};
 use serial_buffer::SerialBuffer;
@@ -213,6 +213,10 @@ impl ConsoleEpollHandler {
                 if in_buffer.is_empty() {
                     break;
                 }
+                if !desc.is_write_only() {
+                    warn!("Skipping device-readable descriptor on receiveq");
+                    continue;
+                }
                 let len = cmp::min(desc.len(), in_buffer.len() as u32);
                 let source_slice = in_buffer.drain(..len as usize).collect::<Vec<u8>>();