From 9bb1222933fc85eaa326bad00a0db9c128e8dade Mon Sep 17 00:00:00 2001
From: bjorn3 <17426603+bjorn3@users.noreply.github.com>
Date: Wed, 6 Mar 2024 21:06:26 +0100
Subject: [PATCH] Fix UB lint in virtio-core

error: casting references to a bigger memory layout than the backing allocation is undefined behavior, even if the reference is unused
   --> virtio-core/src/probe.rs:126:21
    |
86  |         let capability = unsafe { &*(capability.data.as_ptr() as *const PciCapability) };
    |                                    --------------------------------------------------- backing allocation comes from here
...
126 |                     (&*(capability as *const PciCapability as *const PciCapabilityNotify))
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: casting from `transport_pci::PciCapability` (13 bytes) to `transport_pci::PciCapabilityNotify` (17 bytes)
    = note: `#[deny(invalid_reference_casting)]` on by default
---
 virtio-core/src/probe.rs | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/virtio-core/src/probe.rs b/virtio-core/src/probe.rs
index 4f7d48719d..aebd065d04 100644
--- a/virtio-core/src/probe.rs
+++ b/virtio-core/src/probe.rs
@@ -71,7 +71,7 @@ pub fn probe_device(pcid_handle: &mut PcidServerHandle) -> Result<Device, Error>
     let mut notify_addr = None;
     let mut device_addr = None;
 
-    for capability in pcid_handle
+    for raw_capability in pcid_handle
         .get_capabilities()?
         .iter()
         .filter_map(|capability| {
@@ -83,7 +83,7 @@ pub fn probe_device(pcid_handle: &mut PcidServerHandle) -> Result<Device, Error>
         })
     {
         // SAFETY: We have verified that the length of the data is correct.
-        let capability = unsafe { &*(capability.data.as_ptr() as *const PciCapability) };
+        let capability = unsafe { &*(raw_capability.data.as_ptr() as *const PciCapability) };
 
         match capability.cfg_type {
             CfgType::Common | CfgType::Notify | CfgType::Device => {}
@@ -123,7 +123,7 @@ pub fn probe_device(pcid_handle: &mut PcidServerHandle) -> Result<Device, Error>
                 // SAFETY: The capability type is `Notify`, so its safe to access
                 //         the `notify_multiplier` field.
                 let multiplier = unsafe {
-                    (&*(capability as *const PciCapability as *const PciCapabilityNotify))
+                    (&*(raw_capability.data.as_ptr() as *const PciCapability as *const PciCapabilityNotify))
                         .notify_off_multiplier()
                 };
                 notify_addr = Some((address, multiplier));