RustPython · youknowone · Apr 21, 2025 · Apr 21, 2025
diff --git a/stdlib/src/mmap.rs b/stdlib/src/mmap.rs
@@ -23,13 +23,15 @@ mod mmap {
    };
    use crossbeam_utils::atomic::AtomicCell;
    use memmap2::{Advice, Mmap, MmapMut, MmapOptions};
+    #[cfg(unix)]
+    use nix::sys::stat::fstat;
    use nix::unistd;
    use num_traits::Signed;
    use std::fs::File;
-    use std::io::Write;
+    use std::io::{self, Write};
    use std::ops::{Deref, DerefMut};
    #[cfg(unix)]
-    use std::os::unix::io::{FromRawFd, IntoRawFd, RawFd};
+    use std::os::unix::io::{FromRawFd, RawFd};

    fn advice_try_from_i32(vm: &VirtualMachine, i: i32) -> PyResult<Advice> {
        Ok(match i {
@@ -299,7 +301,7 @@ mod mmap {
        fn py_new(
            cls: PyTypeRef,
            MmapNewArgs {
-                fileno: mut fd,
+                fileno: fd,
                length,
                flags,
                prot,
@@ -348,12 +350,10 @@ mod mmap {
            };

            if fd != -1 {
-                let file = unsafe { File::from_raw_fd(fd) };
-                let metadata = file.metadata().map_err(|err| err.to_pyexception(vm))?;
-                let file_len: libc::off_t = metadata.len().try_into().expect("file size overflow");
-                // File::from_raw_fd will consume the fd, so we
-                // have to  get it again.
-                fd = file.into_raw_fd();
+                let metadata = fstat(fd)
+                    .map_err(|err| io::Error::from_raw_os_error(err as i32).to_pyexception(vm))?;
+                let file_len = metadata.st_size;
+
                if map_size == 0 {
                    if file_len == 0 {
                        return Err(vm.new_value_error("cannot mmap an empty file".to_owned()));