From 649f116d9d63ca21059be6cbcee221b4c5a6827f Mon Sep 17 00:00:00 2001
From: Richard Zhang <rizhang@google.com>
Date: Thu, 6 Aug 2020 18:17:04 -0700
Subject: [PATCH] msg_socket: delete impl for Mutex

The MsgOnSocket impl for Mutex contains a threading bug where it's
possible for the object inside the Mutex to mutate after msg_size()
and/or fd_count() has been called.

Also it's not being used.

BUG=b:162032986
TEST=cargo test -p msg_socket

Change-Id: I41188547152236c8124d9ac9593deea93dc02c73
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2339308
Reviewed-by: Zach Reizner <zachr@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Commit-Queue: Richard Zhang <rizhang@google.com>
---
 msg_socket/src/msg_on_socket.rs | 23 -----------------------
 1 file changed, 23 deletions(-)

diff --git a/msg_socket/src/msg_on_socket.rs b/msg_socket/src/msg_on_socket.rs
index 011c2e8786..29ff6d3381 100644
--- a/msg_socket/src/msg_on_socket.rs
+++ b/msg_socket/src/msg_on_socket.rs
@@ -17,7 +17,6 @@ use std::sync::Arc;
 use base::{Error as SysError, EventFd};
 use data_model::*;
 use slice::{slice_read_helper, slice_write_helper};
-use sync::Mutex;
 
 #[derive(Debug)]
 /// An error during transaction or serialization/deserialization.
@@ -190,28 +189,6 @@ impl<T: MsgOnSocket> MsgOnSocket for Option<T> {
     }
 }
 
-impl<T: MsgOnSocket> MsgOnSocket for Mutex<T> {
-    fn uses_fd() -> bool {
-        T::uses_fd()
-    }
-
-    fn msg_size(&self) -> usize {
-        self.lock().msg_size()
-    }
-
-    fn fd_count(&self) -> usize {
-        self.lock().fd_count()
-    }
-
-    unsafe fn read_from_buffer(buffer: &[u8], fds: &[RawFd]) -> MsgResult<(Self, usize)> {
-        T::read_from_buffer(buffer, fds).map(|(v, count)| (Mutex::new(v), count))
-    }
-
-    fn write_to_buffer(&self, buffer: &mut [u8], fds: &mut [RawFd]) -> MsgResult<usize> {
-        self.lock().write_to_buffer(buffer, fds)
-    }
-}
-
 impl<T: MsgOnSocket> MsgOnSocket for Arc<T> {
     fn uses_fd() -> bool {
         T::uses_fd()