Close file descriptors of pipes after use (#2591)

* Close file descriptors of pipes after use

* cat: Test file descriptor exhaustion

* fixup! cat: Test file descriptor exhaustion

src/uu/cat/src/splice.rs

@@ -2,8 +2,9 @@ use super::{CatResult, InputHandle};
 
 use nix::fcntl::{splice, SpliceFFlags};
 use nix::unistd::{self, pipe};
+use std::fs::File;
 use std::io::Read;
-use std::os::unix::io::RawFd;
+use std::os::unix::io::{FromRawFd, RawFd};
 
 const BUF_SIZE: usize = 1024 * 16;
 
@@ -19,13 +20,11 @@ pub(super) fn write_fast_using_splice<R: Read>(
     handle: &mut InputHandle<R>,
     write_fd: RawFd,
 ) -> CatResult<bool> {
-    let (pipe_rd, pipe_wr) = match pipe() {
-        Ok(r) => r,
-        Err(_) => {
-            // It is very rare that creating a pipe fails, but it can happen.
-            return Ok(true);
-        }
-    };
+    let (pipe_rd, pipe_wr) = pipe()?;
+
+    // Ensure the pipe is closed when the function returns.
+    // SAFETY: The file descriptors do not have other owners.
+    let _handles = unsafe { (File::from_raw_fd(pipe_rd), File::from_raw_fd(pipe_wr)) };
 
     loop {
         match splice(

src/uu/wc/src/count_bytes.rs

@@ -1,15 +1,15 @@
 use super::{WcResult, WordCountable};
 
 #[cfg(any(target_os = "linux", target_os = "android"))]
-use std::fs::OpenOptions;
+use std::fs::{File, OpenOptions};
 use std::io::ErrorKind;
 
 #[cfg(unix)]
 use libc::S_IFREG;
 #[cfg(unix)]
 use nix::sys::stat::fstat;
 #[cfg(any(target_os = "linux", target_os = "android"))]
-use std::os::unix::io::{AsRawFd, RawFd};
+use std::os::unix::io::{AsRawFd, FromRawFd, RawFd};
 
 #[cfg(any(target_os = "linux", target_os = "android"))]
 use libc::S_IFIFO;
@@ -47,6 +47,10 @@ fn count_bytes_using_splice(fd: RawFd) -> nix::Result<usize> {
     let null = null_file.as_raw_fd();
     let (pipe_rd, pipe_wr) = pipe()?;
 
+    // Ensure the pipe is closed when the function returns.
+    // SAFETY: The file descriptors do not have other owners.
+    let _handles = unsafe { (File::from_raw_fd(pipe_rd), File::from_raw_fd(pipe_wr)) };
+
     let mut byte_count = 0;
     loop {
         let res = splice(fd, None, pipe_wr, None, BUF_SIZE, SpliceFFlags::empty())?;

tests/by-util/test_cat.rs

@@ -1,8 +1,13 @@
+// spell-checker:ignore NOFILE
+
 use crate::common::util::*;
 use std::fs::OpenOptions;
 #[cfg(unix)]
 use std::io::Read;
 
+#[cfg(target_os = "linux")]
+use rlimit::Resource;
+
 #[test]
 fn test_output_simple() {
     new_ucmd!()
@@ -87,6 +92,23 @@ fn test_fifo_symlink() {
     thread.join().unwrap();
 }
 
+#[test]
+#[cfg(target_os = "linux")]
+fn test_closes_file_descriptors() {
+    // Each file creates a pipe, which has two file descriptors.
+    // If they are not closed then five is certainly too many.
+    new_ucmd!()
+        .args(&[
+            "alpha.txt",
+            "alpha.txt",
+            "alpha.txt",
+            "alpha.txt",
+            "alpha.txt",
+        ])
+        .with_limit(Resource::NOFILE, 9, 9)
+        .succeeds();
+}
+
 #[test]
 #[cfg(unix)]
 fn test_piped_to_regular_file() {