From a77160dca4273467653ca5e2c050e776f6d5fce0 Mon Sep 17 00:00:00 2001
From: Rob Bradford <robert.bradford@intel.com>
Date: Tue, 14 Sep 2021 17:02:20 +0100
Subject: [PATCH] devices: acpi: Increase robustness of bus devices

Check the size of data buffer for reading on the ApciPmTimer device to
avoid a potential panic if the guest uses non-DWORD access.

Simplify the zeroring of the buffer for AcpiShutdownDevice.

Signed-off-by: Rob Bradford <robert.bradford@intel.com>
---
 devices/src/acpi.rs | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/devices/src/acpi.rs b/devices/src/acpi.rs
index b37e7cbea..ece070049 100644
--- a/devices/src/acpi.rs
+++ b/devices/src/acpi.rs
@@ -34,9 +34,7 @@ impl AcpiShutdownDevice {
 impl BusDevice for AcpiShutdownDevice {
     // Spec has all fields as zero
     fn read(&mut self, _base: u64, _offset: u64, data: &mut [u8]) {
-        for i in data.iter_mut() {
-            *i = 0;
-        }
+        data.fill(0)
     }
 
     fn write(&mut self, _base: u64, _offset: u64, data: &[u8]) -> Option<Arc<Barrier>> {
@@ -191,6 +189,10 @@ impl Default for AcpiPmTimerDevice {
 
 impl BusDevice for AcpiPmTimerDevice {
     fn read(&mut self, _base: u64, _offset: u64, data: &mut [u8]) {
+        if data.len() != std::mem::size_of::<u32>() {
+            warn!("Invalid sized read of PM timer: {}", data.len());
+            return;
+        }
         let now = Instant::now();
         let since = now.duration_since(self.start);
         let nanos = since.as_nanos();