mv: fix moving FIFO to a different filesystem

Fix a bug in `mv` where it would hang indefinitely while trying to copy
a FIFO across filesystems. The solution is to remove the old FIFO and
create a new one on the new filesystem.

Fixes #7076

src/uu/mv/Cargo.toml

@@ -21,13 +21,14 @@ path = "src/mv.rs"
 clap = { workspace = true }
 fs_extra = { workspace = true }
 indicatif = { workspace = true }
+libc = { workspace = true }
+thiserror = { workspace = true }
 uucore = { workspace = true, features = [
   "backup-control",
   "fs",
   "fsxattr",
   "update-control",
 ] }
-thiserror = { workspace = true }
 
 [target.'cfg(windows)'.dependencies]
 windows-sys = { workspace = true, features = [

src/uu/mv/src/mv.rs

@@ -10,6 +10,7 @@ mod error;
 use clap::builder::ValueParser;
 use clap::{Arg, ArgAction, ArgMatches, Command, error::ErrorKind};
 use indicatif::{MultiProgress, ProgressBar, ProgressStyle};
+
 use std::collections::HashSet;
 use std::env;
 use std::ffi::OsString;
@@ -17,12 +18,17 @@ use std::fs;
 use std::io;
 #[cfg(unix)]
 use std::os::unix;
+#[cfg(unix)]
+use std::os::unix::fs::FileTypeExt;
 #[cfg(windows)]
 use std::os::windows;
 use std::path::{Path, PathBuf, absolute};
+
 use uucore::backup_control::{self, source_is_target_backup};
 use uucore::display::Quotable;
 use uucore::error::{FromIo, UResult, USimpleError, UUsageError, set_exit_code};
+#[cfg(unix)]
+use uucore::fs::make_fifo;
 use uucore::fs::{
     MissingHandling, ResolveMode, are_hardlinks_or_one_way_symlink_to_same_file,
     are_hardlinks_to_same_file, canonicalize, path_ends_with_terminator,
@@ -665,6 +671,16 @@ fn rename(
     Ok(())
 }
 
+#[cfg(unix)]
+fn is_fifo(filetype: fs::FileType) -> bool {
+    filetype.is_fifo()
+}
+
+#[cfg(not(unix))]
+fn is_fifo(_filetype: fs::FileType) -> bool {
+    false
+}
+
 /// A wrapper around `fs::rename`, so that if it fails, we try falling back on
 /// copying and removing.
 fn rename_with_fallback(
@@ -694,12 +710,28 @@ fn rename_with_fallback(
             rename_symlink_fallback(from, to)
         } else if file_type.is_dir() {
             rename_dir_fallback(from, to, multi_progress)
+        } else if is_fifo(file_type) {
+            rename_fifo_fallback(from, to)
         } else {
             rename_file_fallback(from, to)
         }
     })
 }
 
+/// Replace the destination with a new pipe with the same name as the source.
+#[cfg(unix)]
+fn rename_fifo_fallback(from: &Path, to: &Path) -> io::Result<()> {
+    if to.try_exists()? {
+        fs::remove_file(to)?;
+    }
+    make_fifo(to).and_then(|_| fs::remove_file(from))
+}
+
+#[cfg(not(unix))]
+fn rename_fifo_fallback(_from: &Path, _to: &Path) -> io::Result<()> {
+    Ok(())
+}
+
 /// Move the given symlink to the given destination. On Windows, dangling
 /// symlinks return an error.
 #[cfg(unix)]

tests/by-util/test_mv.rs

@@ -7,6 +7,8 @@
 use filetime::FileTime;
 use rstest::rstest;
 use std::io::Write;
+#[cfg(not(windows))]
+use std::path::Path;
 use uutests::new_ucmd;
 use uutests::util::TestScenario;
 use uutests::{at_and_ucmd, util_name};
@@ -1876,3 +1878,18 @@ fn test_mv_error_msg_with_multiple_sources_that_does_not_exist() {
         .stderr_contains("mv: cannot stat 'a': No such file or directory")
         .stderr_contains("mv: cannot stat 'b/': No such file or directory");
 }
+
+#[cfg(not(windows))]
+#[ignore = "requires access to a different filesystem"]
+#[test]
+fn test_special_file_different_filesystem() {
+    let (at, mut ucmd) = at_and_ucmd!();
+    at.mkfifo("f");
+    // TODO Use `TestScenario::mount_temp_fs()` for this purpose and
+    // un-ignore this test.
+    std::fs::create_dir("/dev/shm/tmp").unwrap();
+    ucmd.args(&["f", "/dev/shm/tmp"]).succeeds().no_output();
+    assert!(!at.file_exists("f"));
+    assert!(Path::new("/dev/shm/tmp/f").exists());
+    std::fs::remove_dir_all("/dev/shm/tmp").unwrap();
+}