feat: I/O safety pipe, pipe2 & write

Author: JonathanWoollett-Light

src/pty.rs

@@ -71,7 +71,7 @@ impl io::Read for PtyMaster {
 
 impl io::Write for PtyMaster {
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
-        unistd::write(self.0.as_raw_fd(), buf).map_err(io::Error::from)
+        unistd::write(&self.0, buf).map_err(io::Error::from)
     }
     fn flush(&mut self) -> io::Result<()> {
         Ok(())
@@ -86,7 +86,7 @@ impl io::Read for &PtyMaster {
 
 impl io::Write for &PtyMaster {
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
-        unistd::write(self.0.as_raw_fd(), buf).map_err(io::Error::from)
+        unistd::write(&self.0, buf).map_err(io::Error::from)
     }
     fn flush(&mut self) -> io::Result<()> {
         Ok(())

src/sys/epoll.rs

@@ -87,7 +87,7 @@ impl EpollEvent {
 /// epoll.add(&eventfd, EpollEvent::new(EpollFlags::EPOLLIN,DATA))?;
 ///
 /// // Arm eventfd & Time wait
-/// write(eventfd.as_raw_fd(), &1u64.to_ne_bytes())?;
+/// write(&eventfd, &1u64.to_ne_bytes())?;
 /// let now = Instant::now();
 ///
 /// // Wait on event

src/sys/select.rs

@@ -322,8 +322,8 @@ where
 mod tests {
     use super::*;
     use crate::sys::time::{TimeVal, TimeValLike};
-    use crate::unistd::{close, pipe, write};
-    use std::os::unix::io::{FromRawFd, OwnedFd, RawFd};
+    use crate::unistd::{pipe, write};
+    use std::os::unix::io::RawFd;
 
     #[test]
     fn fdset_insert() {
@@ -466,12 +466,9 @@ mod tests {
     #[test]
     fn test_select() {
         let (r1, w1) = pipe().unwrap();
-        let r1 = unsafe { OwnedFd::from_raw_fd(r1) };
-        let w1 = unsafe { OwnedFd::from_raw_fd(w1) };
         let (r2, _w2) = pipe().unwrap();
-        let r2 = unsafe { OwnedFd::from_raw_fd(r2) };
 
-        write(w1.as_raw_fd(), b"hi!").unwrap();
+        write(&w1, b"hi!").unwrap();
         let mut fd_set = FdSet::new();
         fd_set.insert(&r1);
         fd_set.insert(&r2);
@@ -483,18 +480,14 @@ mod tests {
         );
         assert!(fd_set.contains(&r1));
         assert!(!fd_set.contains(&r2));
-        close(_w2).unwrap();
     }
 
     #[test]
     fn test_select_nfds() {
         let (r1, w1) = pipe().unwrap();
         let (r2, _w2) = pipe().unwrap();
-        let r1 = unsafe { OwnedFd::from_raw_fd(r1) };
-        let w1 = unsafe { OwnedFd::from_raw_fd(w1) };
-        let r2 = unsafe { OwnedFd::from_raw_fd(r2) };
 
-        write(w1.as_raw_fd(), b"hi!").unwrap();
+        write(&w1, b"hi!").unwrap();
         let mut fd_set = FdSet::new();
         fd_set.insert(&r1);
         fd_set.insert(&r2);
@@ -521,16 +514,13 @@ mod tests {
         }
         assert!(fd_set.contains(&r1));
         assert!(!fd_set.contains(&r2));
-        close(_w2).unwrap();
     }
 
     #[test]
     fn test_select_nfds2() {
         let (r1, w1) = pipe().unwrap();
-        write(w1, b"hi!").unwrap();
+        write(&w1, b"hi!").unwrap();
         let (r2, _w2) = pipe().unwrap();
-        let r1 = unsafe { OwnedFd::from_raw_fd(r1) };
-        let r2 = unsafe { OwnedFd::from_raw_fd(r2) };
         let mut fd_set = FdSet::new();
         fd_set.insert(&r1);
         fd_set.insert(&r2);
@@ -549,6 +539,5 @@ mod tests {
         );
         assert!(fd_set.contains(&r1));
         assert!(!fd_set.contains(&r2));
-        close(_w2).unwrap();
     }
 }

src/sys/socket/mod.rs

@@ -1479,7 +1479,7 @@ impl<'a> ControlMessage<'a> {
 /// let (r, w) = pipe().unwrap();
 ///
 /// let iov = [IoSlice::new(b"hello")];
-/// let fds = [r];
+/// let fds = [r.as_raw_fd()];
 /// let cmsg = ControlMessage::ScmRights(&fds);
 /// sendmsg::<()>(fd1.as_raw_fd(), &iov, &[cmsg], MsgFlags::empty(), None).unwrap();
 /// ```
@@ -1496,7 +1496,7 @@ impl<'a> ControlMessage<'a> {
 /// let (r, w) = pipe().unwrap();
 ///
 /// let iov = [IoSlice::new(b"hello")];
-/// let fds = [r];
+/// let fds = [r.as_raw_fd()];
 /// let cmsg = ControlMessage::ScmRights(&fds);
 /// sendmsg(fd.as_raw_fd(), &iov, &[cmsg], MsgFlags::empty(), Some(&localhost)).unwrap();
 /// ```

src/unistd.rs

@@ -35,7 +35,7 @@ use std::ffi::{CString, OsStr};
 use std::os::unix::ffi::OsStrExt;
 use std::os::unix::ffi::OsStringExt;
 use std::os::unix::io::RawFd;
-use std::os::unix::io::{AsFd, AsRawFd};
+use std::os::unix::io::{AsFd, AsRawFd, OwnedFd};
 use std::path::PathBuf;
 use std::{fmt, mem, ptr};
 
@@ -260,7 +260,7 @@ impl ForkResult {
 ///    }
 ///    Ok(ForkResult::Child) => {
 ///        // Unsafe to use `println!` (or `unwrap`) here. See Safety.
-///        write(libc::STDOUT_FILENO, "I'm a new child process\n".as_bytes()).ok();
+///        write(std::io::stdout(), "I'm a new child process\n".as_bytes()).ok();
 ///        unsafe { libc::_exit(0) };
 ///    }
 ///    Err(_) => println!("Fork failed"),
@@ -1115,9 +1115,13 @@ pub fn read(fd: RawFd, buf: &mut [u8]) -> Result<usize> {
 /// Write to a raw file descriptor.
 ///
 /// See also [write(2)](https://pubs.opengroup.org/onlinepubs/9699919799/functions/write.html)
-pub fn write(fd: RawFd, buf: &[u8]) -> Result<usize> {
+pub fn write<Fd: AsFd>(fd: Fd, buf: &[u8]) -> Result<usize> {
     let res = unsafe {
-        libc::write(fd, buf.as_ptr() as *const c_void, buf.len() as size_t)
+        libc::write(
+            fd.as_fd().as_raw_fd(),
+            buf.as_ptr() as *const c_void,
+            buf.len() as size_t,
+        )
     };
 
     Errno::result(res).map(|r| r as usize)
@@ -1189,14 +1193,15 @@ pub fn lseek64(
 /// Create an interprocess channel.
 ///
 /// See also [pipe(2)](https://pubs.opengroup.org/onlinepubs/9699919799/functions/pipe.html)
-pub fn pipe() -> std::result::Result<(RawFd, RawFd), Error> {
-    let mut fds = mem::MaybeUninit::<[c_int; 2]>::uninit();
+pub fn pipe() -> std::result::Result<(OwnedFd, OwnedFd), Error> {
+    let mut fds = mem::MaybeUninit::<[OwnedFd; 2]>::uninit();
 
     let res = unsafe { libc::pipe(fds.as_mut_ptr() as *mut c_int) };
 
     Error::result(res)?;
 
-    unsafe { Ok((fds.assume_init()[0], fds.assume_init()[1])) }
+    let [read, write] = unsafe { fds.assume_init() };
+    Ok((read, write))
 }
 
 feature! {
@@ -1230,15 +1235,16 @@ feature! {
     target_os = "openbsd",
     target_os = "solaris"
 ))]
-pub fn pipe2(flags: OFlag) -> Result<(RawFd, RawFd)> {
-    let mut fds = mem::MaybeUninit::<[c_int; 2]>::uninit();
+pub fn pipe2(flags: OFlag) -> Result<(OwnedFd, OwnedFd)> {
+    let mut fds = mem::MaybeUninit::<[OwnedFd; 2]>::uninit();
 
     let res =
         unsafe { libc::pipe2(fds.as_mut_ptr() as *mut c_int, flags.bits()) };
 
     Errno::result(res)?;
 
-    unsafe { Ok((fds.assume_init()[0], fds.assume_init()[1])) }
+    let [read, write] = unsafe { fds.assume_init() };
+    Ok((read, write))
 }
 
 /// Truncate a file to a specified length

test/sys/test_select.rs

@@ -2,17 +2,15 @@ use nix::sys::select::*;
 use nix::sys::signal::SigSet;
 use nix::sys::time::{TimeSpec, TimeValLike};
 use nix::unistd::{pipe, write};
-use std::os::unix::io::{AsRawFd, BorrowedFd, FromRawFd, OwnedFd};
+use std::os::unix::io::{AsRawFd, BorrowedFd};
 
 #[test]
 pub fn test_pselect() {
     let _mtx = crate::SIGNAL_MTX.lock();
 
     let (r1, w1) = pipe().unwrap();
-    write(w1, b"hi!").unwrap();
-    let r1 = unsafe { OwnedFd::from_raw_fd(r1) };
+    write(&w1, b"hi!").unwrap();
     let (r2, _w2) = pipe().unwrap();
-    let r2 = unsafe { OwnedFd::from_raw_fd(r2) };
 
     let mut fd_set = FdSet::new();
     fd_set.insert(&r1);
@@ -31,10 +29,8 @@ pub fn test_pselect() {
 #[test]
 pub fn test_pselect_nfds2() {
     let (r1, w1) = pipe().unwrap();
-    write(w1, b"hi!").unwrap();
-    let r1 = unsafe { OwnedFd::from_raw_fd(r1) };
+    write(&w1, b"hi!").unwrap();
     let (r2, _w2) = pipe().unwrap();
-    let r2 = unsafe { OwnedFd::from_raw_fd(r2) };
 
     let mut fd_set = FdSet::new();
     fd_set.insert(&r1);

test/sys/test_socket.rs

@@ -200,7 +200,7 @@ pub fn test_socketpair() {
         SockFlag::empty(),
     )
     .unwrap();
-    write(fd1.as_raw_fd(), b"hello").unwrap();
+    write(&fd1, b"hello").unwrap();
     let mut buf = [0; 5];
     read(fd2.as_raw_fd(), &mut buf).unwrap();
 
@@ -757,7 +757,7 @@ pub fn test_scm_rights() {
 
     {
         let iov = [IoSlice::new(b"hello")];
-        let fds = [r];
+        let fds = [r.as_raw_fd()];
         let cmsg = ControlMessage::ScmRights(&fds);
         assert_eq!(
             sendmsg::<()>(
@@ -770,7 +770,6 @@ pub fn test_scm_rights() {
             .unwrap(),
             5
         );
-        close(r).unwrap();
     }
 
     {
@@ -803,12 +802,11 @@ pub fn test_scm_rights() {
 
     let received_r = received_r.expect("Did not receive passed fd");
     // Ensure that the received file descriptor works
-    write(w.as_raw_fd(), b"world").unwrap();
+    write(&w, b"world").unwrap();
     let mut buf = [0u8; 5];
     read(received_r.as_raw_fd(), &mut buf).unwrap();
     assert_eq!(&buf[..], b"world");
     close(received_r).unwrap();
-    close(w).unwrap();
 }
 
 // Disable the test on emulated platforms due to not enabled support of AF_ALG in QEMU from rust cross
@@ -1451,7 +1449,7 @@ fn test_impl_scm_credentials_and_rights(mut space: Vec<u8>) {
             gid: getgid().as_raw(),
         }
         .into();
-        let fds = [r];
+        let fds = [r.as_raw_fd()];
         let cmsgs = [
             ControlMessage::ScmCredentials(&cred),
             ControlMessage::ScmRights(&fds),
@@ -1467,7 +1465,6 @@ fn test_impl_scm_credentials_and_rights(mut space: Vec<u8>) {
             .unwrap(),
             5
         );
-        close(r).unwrap();
     }
 
     {
@@ -1510,12 +1507,11 @@ fn test_impl_scm_credentials_and_rights(mut space: Vec<u8>) {
 
     let received_r = received_r.expect("Did not receive passed fd");
     // Ensure that the received file descriptor works
-    write(w.as_raw_fd(), b"world").unwrap();
+    write(&w, b"world").unwrap();
     let mut buf = [0u8; 5];
     read(received_r.as_raw_fd(), &mut buf).unwrap();
     assert_eq!(&buf[..], b"world");
     close(received_r).unwrap();
-    close(w).unwrap();
 }
 
 // Test creating and using named unix domain sockets
@@ -1548,7 +1544,7 @@ pub fn test_named_unixdomain() {
         )
         .expect("socket failed");
         connect(s2.as_raw_fd(), &sockaddr).expect("connect failed");
-        write(s2.as_raw_fd(), b"hello").expect("write failed");
+        write(&s2, b"hello").expect("write failed");
     });
 
     let s3 = accept(s1.as_raw_fd()).expect("accept failed");

test/sys/test_sockopt.rs

@@ -5,7 +5,7 @@ use nix::sys::socket::{
     SockProtocol, SockType,
 };
 use rand::{thread_rng, Rng};
-use std::os::unix::io::AsRawFd;
+use std::os::unix::io::{AsRawFd, FromRawFd, OwnedFd};
 
 // NB: FreeBSD supports LOCAL_PEERCRED for SOCK_SEQPACKET, but OSX does not.
 #[cfg(any(target_os = "dragonfly", target_os = "freebsd",))]
@@ -151,7 +151,8 @@ fn test_so_tcp_maxseg() {
     .unwrap();
     connect(ssock.as_raw_fd(), &sock_addr).unwrap();
     let rsess = accept(rsock.as_raw_fd()).unwrap();
-    write(rsess, b"hello").unwrap();
+    let rsess = unsafe { OwnedFd::from_raw_fd(rsess) };
+    write(&rsess, b"hello").unwrap();
     let actual = getsockopt(&ssock, sockopt::TcpMaxSeg).unwrap();
     // Actual max segment size takes header lengths into account, max IPv4 options (60 bytes) + max
     // TCP options (40 bytes) are subtracted from the requested maximum as a lower boundary.
@@ -185,7 +186,6 @@ fn test_so_type() {
 #[test]
 fn test_so_type_unknown() {
     use nix::errno::Errno;
-    use std::os::unix::io::{FromRawFd, OwnedFd};
 
     require_capability!("test_so_type", CAP_NET_RAW);
     let raw_fd = unsafe { libc::socket(libc::AF_PACKET, libc::SOCK_PACKET, 0) };

test/sys/test_termios.rs

@@ -11,7 +11,7 @@ use nix::unistd::{read, write};
 fn write_all<Fd: AsFd>(f: Fd, buf: &[u8]) {
     let mut len = 0;
     while len < buf.len() {
-        len += write(f.as_fd().as_raw_fd(), &buf[len..]).unwrap();
+        len += write(f.as_fd(), &buf[len..]).unwrap();
     }
 }