From bc6acb842f1ebb263245cd95fe5a92fe5f350bd3 Mon Sep 17 00:00:00 2001
From: Changyuan Lyu <changyuanl@google.com>
Date: Fri, 12 Jul 2024 22:54:12 -0700
Subject: [PATCH] block: fix `status` value size

As per VirtIO spec 1.2 section 5.2.6, the `status` field is a byte, not
u32. cloud-hypervisor writes an `u32` to guest memory, which
accidentally zeros out the following 3 bytes, and may corrupt guest OS
internal state.

Signed-off-by: Changyuan Lyu <changyuanl@google.com>
---
 block/src/lib.rs            | 7 ++++---
 vhost_user_block/src/lib.rs | 2 +-
 virtio-devices/src/block.rs | 4 ++--
 3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/block/src/lib.rs b/block/src/lib.rs
index 8fb2e91a8..d512aae85 100644
--- a/block/src/lib.rs
+++ b/block/src/lib.rs
@@ -164,8 +164,8 @@ pub enum ExecuteError {
 }
 
 impl ExecuteError {
-    pub fn status(&self) -> u32 {
-        match *self {
+    pub fn status(&self) -> u8 {
+        let status = match *self {
             ExecuteError::BadRequest(_) => VIRTIO_BLK_S_IOERR,
             ExecuteError::Flush(_) => VIRTIO_BLK_S_IOERR,
             ExecuteError::Read(_) => VIRTIO_BLK_S_IOERR,
@@ -180,7 +180,8 @@ impl ExecuteError {
             ExecuteError::AsyncWrite(_) => VIRTIO_BLK_S_IOERR,
             ExecuteError::AsyncFlush(_) => VIRTIO_BLK_S_IOERR,
             ExecuteError::TemporaryBufferAllocation(_) => VIRTIO_BLK_S_IOERR,
-        }
+        };
+        status as u8
     }
 }
 
diff --git a/vhost_user_block/src/lib.rs b/vhost_user_block/src/lib.rs
index 8f70bc678..f779fb222 100644
--- a/vhost_user_block/src/lib.rs
+++ b/vhost_user_block/src/lib.rs
@@ -148,7 +148,7 @@ impl VhostUserBlkThread {
                     ) {
                         Ok(l) => {
                             len = l;
-                            VIRTIO_BLK_S_OK
+                            VIRTIO_BLK_S_OK as u8
                         }
                         Err(e) => {
                             len = 1;
diff --git a/virtio-devices/src/block.rs b/virtio-devices/src/block.rs
index b8302bbe2..95411bb4d 100644
--- a/virtio-devices/src/block.rs
+++ b/virtio-devices/src/block.rs
@@ -215,7 +215,7 @@ impl BlockEpollHandler {
             } else {
                 desc_chain
                     .memory()
-                    .write_obj(VIRTIO_BLK_S_OK, request.status_addr)
+                    .write_obj(VIRTIO_BLK_S_OK as u8, request.status_addr)
                     .map_err(Error::RequestStatus)?;
 
                 // If no asynchronous operation has been submitted, we can
@@ -361,7 +361,7 @@ impl BlockEpollHandler {
                     .write_latency_avg
                     .store(write_avg, Ordering::Relaxed);
 
-                (VIRTIO_BLK_S_OK, result as u32)
+                (VIRTIO_BLK_S_OK as u8, result as u32)
             } else {
                 error!(
                     "Request failed: {:x?} {:?}",