From 8a4b3efec9cea7eaee84fe8320a679ee6ef2c456 Mon Sep 17 00:00:00 2001
From: Rob Bradford <rbradford@meta.com>
Date: Sat, 25 Apr 2026 22:07:27 +0100
Subject: [PATCH] devices: acpi: Reject mis-sized accesses to shutdown and GED
 devices

These devices should only be accessed by single byte accesses as
specified through the ACPI definitions for them.

Signed-off-by: Rob Bradford <rbradford@meta.com>
Assisted-by: Claude:Opus-4.7
---
 devices/src/acpi.rs | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/devices/src/acpi.rs b/devices/src/acpi.rs
index 54b8ca76a..2d7f49a73 100644
--- a/devices/src/acpi.rs
+++ b/devices/src/acpi.rs
@@ -45,10 +45,21 @@ impl AcpiShutdownDevice {
 impl BusDevice for AcpiShutdownDevice {
     // Spec has all fields as zero
     fn read(&mut self, _base: u64, _offset: u64, data: &mut [u8]) {
+        if data.len() != 1 {
+            warn!("Invalid sized read of ACPI shutdown device: {}", data.len());
+            return;
+        }
         data.fill(0);
     }
 
     fn write(&mut self, _base: u64, _offset: u64, data: &[u8]) -> Option<Arc<Barrier>> {
+        if data.len() != 1 {
+            warn!(
+                "Invalid sized write of ACPI shutdown device: {}",
+                data.len()
+            );
+            return None;
+        }
         if data[0] == 1 {
             info!("ACPI Reboot signalled");
             if let Err(e) = self.reset_evt.write(1) {
@@ -119,6 +130,10 @@ impl AcpiGedDevice {
 impl BusDevice for AcpiGedDevice {
     // Spec has all fields as zero
     fn read(&mut self, _base: u64, _offset: u64, data: &mut [u8]) {
+        if data.len() != 1 {
+            warn!("Invalid sized read of ACPI GED device: {}", data.len());
+            return;
+        }
         data[0] = self.notification_type.bits();
         self.notification_type = AcpiNotificationFlags::NO_DEVICES_CHANGED;
     }