From 850090d99c81dde7615e2a7e2111c09650868a48 Mon Sep 17 00:00:00 2001
From: Thom Chiovoloni <thom@shift.click>
Date: Mon, 5 Sep 2022 08:37:20 -0700
Subject: [PATCH] Avoid UB in the Windows filesystem code in... bootstrap?

---
 src/bootstrap/Cargo.toml |  1 +
 src/bootstrap/util.rs    | 10 ++++++----
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/src/bootstrap/Cargo.toml b/src/bootstrap/Cargo.toml
index 2dad41bb18f..95e71173773 100644
--- a/src/bootstrap/Cargo.toml
+++ b/src/bootstrap/Cargo.toml
@@ -67,6 +67,7 @@ features = [
     "psapi",
     "impl-default",
     "timezoneapi",
+    "winbase",
 ]
 
 [dev-dependencies]
diff --git a/src/bootstrap/util.rs b/src/bootstrap/util.rs
index 3a00e258e00..0ebabbd5ca5 100644
--- a/src/bootstrap/util.rs
+++ b/src/bootstrap/util.rs
@@ -197,9 +197,11 @@ pub fn symlink_dir(config: &Config, src: &Path, dest: &Path) -> io::Result<()> {
                 ptr::null_mut(),
             );
 
-            let mut data = [0u8; MAXIMUM_REPARSE_DATA_BUFFER_SIZE as usize];
-            let db = data.as_mut_ptr() as *mut REPARSE_MOUNTPOINT_DATA_BUFFER;
-            let buf = &mut (*db).ReparseTarget as *mut u16;
+            #[repr(C, align(8))]
+            struct Align8<T>(T);
+            let mut data = Align8([0u8; MAXIMUM_REPARSE_DATA_BUFFER_SIZE as usize]);
+            let db = data.0.as_mut_ptr() as *mut REPARSE_MOUNTPOINT_DATA_BUFFER;
+            let buf = core::ptr::addr_of_mut!((*db).ReparseTarget) as *mut u16;
             let mut i = 0;
             // FIXME: this conversion is very hacky
             let v = br"\??\";
@@ -219,7 +221,7 @@ pub fn symlink_dir(config: &Config, src: &Path, dest: &Path) -> io::Result<()> {
             let res = DeviceIoControl(
                 h as *mut _,
                 FSCTL_SET_REPARSE_POINT,
-                data.as_ptr() as *mut _,
+                db.cast(),
                 (*db).ReparseDataLength + 8,
                 ptr::null_mut(),
                 0,