From 48123669b59e53fa1e150b42028d7dccbf296158 Mon Sep 17 00:00:00 2001
From: Rob Bradford <rbradford@meta.com>
Date: Wed, 6 May 2026 15:08:11 +0100
Subject: [PATCH] virtio-devices: console: Skip device-writable output
 descriptors

The output queue handler read data from every descriptor without
checking the write-only flag. The driver must not put device-writable
buffers in the transmitq. 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 | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/virtio-devices/src/console.rs b/virtio-devices/src/console.rs
index 2abf44639..4e157a55a 100644
--- a/virtio-devices/src/console.rs
+++ b/virtio-devices/src/console.rs
@@ -261,6 +261,10 @@ impl ConsoleEpollHandler {
 
         while let Some(mut desc_chain) = trans_queue.pop_descriptor_chain(self.mem.memory()) {
             while let Some(desc) = desc_chain.next() {
+                if desc.is_write_only() {
+                    warn!("Skipping device-writable descriptor on transmitq");
+                    continue;
+                }
                 if let Some(out) = &mut self.out {
                     let mut buf: Vec<u8> = Vec::new();
                     desc_chain