[release-branch.go1.21] internal/syscall/windows: fix the signature of SetFileInformationByHandle

Also fix its call site in internal/poll to pass the length of the
actual buffer instead of an unrelated variable, and update the
definition of FILE_BASIC_INFO to match the documented field types
and add padding that is empirically needed on the 386 architecture.

Passing a pointer to a Go-allocated buffer as type uintptr violates
the unsafe.Pointer conversion rules, which allow such a conversion
only in the call expression itself for a call to syscall.Syscall or
equivalent. That can allow the buffer to be corrupted arbitrarily if
the Go runtime happens to garbage-collect it while the call to
SetFileInformationByHandle is in progress.

The Microsoft documentation for SetFileInformationByHandle specifies
its third argument type as LPVOID, which corresponds to Go's
unsafe.Pointer, not uintptr.

Fixes #65882.
Updates #58933.

Change-Id: If577b57adea9922f5fcca55e46030c703d8f035c
Cq-Include-Trybots: luci.golang.try:go1.21-windows-amd64-longtest
Reviewed-on: https://go-review.googlesource.com/c/go/+/549256
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Than McIntosh <[email protected]>
Auto-Submit: Bryan Mills <[email protected]>
Reviewed-by: Quim Muntal <[email protected]>
Reviewed-by: Alex Brainman <[email protected]>
(cherry picked from commit a709724)
Reviewed-on: https://go-review.googlesource.com/c/go/+/566155
Reviewed-by: Bryan Mills <[email protected]>

Author: Bryan C. Mills

src/internal/poll/fd_windows.go

@@ -1037,8 +1037,7 @@ func (fd *FD) Fchmod(mode uint32) error {
 
 	var du windows.FILE_BASIC_INFO
 	du.FileAttributes = attrs
-	l := uint32(unsafe.Sizeof(d))
-	return windows.SetFileInformationByHandle(fd.Sysfd, windows.FileBasicInfo, uintptr(unsafe.Pointer(&du)), l)
+	return windows.SetFileInformationByHandle(fd.Sysfd, windows.FileBasicInfo, unsafe.Pointer(&du), uint32(unsafe.Sizeof(du)))
 }
 
 // Fchdir wraps syscall.Fchdir.

src/internal/syscall/windows/syscall_windows.go

@@ -129,11 +129,22 @@ type SecurityAttributes struct {
 }
 
 type FILE_BASIC_INFO struct {
-	CreationTime   syscall.Filetime
-	LastAccessTime syscall.Filetime
-	LastWriteTime  syscall.Filetime
-	ChangedTime    syscall.Filetime
+	CreationTime   int64
+	LastAccessTime int64
+	LastWriteTime  int64
+	ChangedTime    int64
 	FileAttributes uint32
+
+	// Pad out to 8-byte alignment.
+	//
+	// Without this padding, TestChmod fails due to an argument validation error
+	// in SetFileInformationByHandle on windows/386.
+	//
+	// https://learn.microsoft.com/en-us/cpp/build/reference/zp-struct-member-alignment?view=msvc-170
+	// says that “The C/C++ headers in the Windows SDK assume the platform's
+	// default alignment is used.” What we see here is padding rather than
+	// alignment, but maybe it is related.
+	_ uint32
 }
 
 const (
@@ -150,7 +161,7 @@ const (
 //sys	GetComputerNameEx(nameformat uint32, buf *uint16, n *uint32) (err error) = GetComputerNameExW
 //sys	MoveFileEx(from *uint16, to *uint16, flags uint32) (err error) = MoveFileExW
 //sys	GetModuleFileName(module syscall.Handle, fn *uint16, len uint32) (n uint32, err error) = kernel32.GetModuleFileNameW
-//sys	SetFileInformationByHandle(handle syscall.Handle, fileInformationClass uint32, buf uintptr, bufsize uint32) (err error) = kernel32.SetFileInformationByHandle
+//sys	SetFileInformationByHandle(handle syscall.Handle, fileInformationClass uint32, buf unsafe.Pointer, bufsize uint32) (err error) = kernel32.SetFileInformationByHandle
 //sys	VirtualQuery(address uintptr, buffer *MemoryBasicInformation, length uintptr) (err error) = kernel32.VirtualQuery
 //sys	GetTempPath2(buflen uint32, buf *uint16) (n uint32, err error) = GetTempPath2W