Bytes: Fix read() and write()

read() and write() must not ignore the `count` parameter: The mappings
passed into the `try_access()` closure are only valid for up to `count`
bytes, not more.

Signed-off-by: Hanna Czenczek <[email protected]>

Author: XanClic

src/guest_memory.rs

@@ -591,8 +591,8 @@ impl<T: GuestMemory + ?Sized> Bytes<GuestAddress> for T {
         self.try_access(
             buf.len(),
             addr,
-            |offset, _count, caddr, region| -> Result<usize> {
-                region.write(&buf[offset..], caddr)
+            |offset, count, caddr, region| -> Result<usize> {
+                region.write(&buf[offset..(offset + count)], caddr)
             },
         )
     }
@@ -601,8 +601,8 @@ impl<T: GuestMemory + ?Sized> Bytes<GuestAddress> for T {
         self.try_access(
             buf.len(),
             addr,
-            |offset, _count, caddr, region| -> Result<usize> {
-                region.read(&mut buf[offset..], caddr)
+            |offset, count, caddr, region| -> Result<usize> {
+                region.read(&mut buf[offset..(offset + count)], caddr)
             },
         )
     }