fix(utils): improve safety of media loader and utf-16 handling

src/utils.rs

@@ -280,11 +280,14 @@ pub fn utf16_bytes_to_cstring16(bytes: &[u8]) -> Result<CString16> {
         bail!("utf16 bytes must be a multiple of 2");
     }
 
-    // SAFETY: reinterpret &[u8] as &[u16].
-    // We just validated it has the right length.
-    let ptr = bytes.as_ptr() as *const u16;
-    let len = bytes.len() / 2;
-    let utf16 = unsafe { std::slice::from_raw_parts(ptr, len) };
+    // Convert the bytes to UTF-16 data.
+    let data = bytes
+        // Chunk everything into two bytes.
+        .chunks_exact(2)
+        // Reinterpret the bytes as u16 little-endian.
+        .map(|chunk| u16::from_le_bytes([chunk[0], chunk[1]]))
+        // Collect the result into a vector.
+        .collect::<Vec<_>>();
 
-    CString16::try_from(utf16.to_vec()).context("unable to convert utf16 bytes to CString16")
+    CString16::try_from(data).context("unable to convert utf16 bytes to CString16")
 }

src/utils/media_loader.rs

@@ -33,8 +33,6 @@ struct MediaLoaderProtocol {
 /// You MUST call [MediaLoaderHandle::unregister] when ready to unregister.
 /// [Drop] is not implemented for this type.
 pub struct MediaLoaderHandle {
-    /// The vendor GUID of the media loader.
-    guid: Guid,
     /// The handle of the media loader in the UEFI stack.
     handle: Handle,
     /// The protocol interface pointer.
@@ -229,7 +227,6 @@ impl MediaLoaderHandle {
 
         // Return a handle to the media loader.
         Ok(Self {
-            guid,
             handle: primary_handle,
             protocol,
             path,
@@ -239,13 +236,8 @@ impl MediaLoaderHandle {
     /// Unregisters a media loader from the UEFI stack.
     /// This will free the memory allocated by the passed data.
     pub fn unregister(self) -> Result<()> {
-        // Check if the media loader is registered.
-        // If it is not, we don't need to do anything.
-        if !Self::already_registered(self.guid)? {
-            return Ok(());
-        }
-
-        // SAFETY: We know that the media loader is registered, so we can safely uninstall it.
+        // SAFETY: We know that the media loader is registered if the handle is valid,
+        // so we can safely uninstall it.
         // We should have allocated the pointers involved, so we can safely free them.
         unsafe {
             // Uninstall the protocol interface for the device path protocol.