cp: fix cp -f f loop when loop is a symlink loop

Fix: tests/cp/thru-dangling.sh

src/uu/cp/src/cp.rs

@@ -38,7 +38,8 @@ use uucore::backup_control::{self, BackupMode};
 use uucore::display::Quotable;
 use uucore::error::{set_exit_code, UClapError, UError, UResult, UUsageError};
 use uucore::fs::{
-    canonicalize, paths_refer_to_same_file, FileInformation, MissingHandling, ResolveMode,
+    canonicalize, is_symlink_loop, paths_refer_to_same_file, FileInformation, MissingHandling,
+    ResolveMode,
 };
 use uucore::{crash, format_usage, help_about, help_usage, prompt_yes, show_error, show_warning};
 
@@ -1388,11 +1389,10 @@ fn handle_existing_dest(
             backup_dest(dest, &backup_path)?;
         }
     }
-
     match options.overwrite {
         // FIXME: print that the file was removed if --verbose is enabled
         OverwriteMode::Clobber(ClobberMode::Force) => {
-            if fs::metadata(dest)?.permissions().readonly() {
+            if is_symlink_loop(dest) || fs::metadata(dest)?.permissions().readonly() {
                 fs::remove_file(dest)?;
             }
         }
@@ -1498,6 +1498,7 @@ fn copy_file(
                 options.overwrite,
                 OverwriteMode::Clobber(ClobberMode::RemoveDestination)
             )
+            && !is_symlink_loop(dest)
             && std::env::var_os("POSIXLY_CORRECT").is_none()
         {
             return Err(Error::Error(format!(

tests/by-util/test_cp.rs

@@ -2309,6 +2309,20 @@ fn test_remove_destination_symbolic_link_loop() {
     assert!(at.file_exists("loop"));
 }
 
+#[test]
+#[cfg(not(windows))]
+fn test_cp_symbolic_link_loop() {
+    let (at, mut ucmd) = at_and_ucmd!();
+    at.symlink_file("loop", "loop");
+    at.plus("loop");
+    at.touch("f");
+    ucmd.args(&["-f", "f", "loop"])
+        .succeeds()
+        .no_stdout()
+        .no_stderr();
+    assert!(at.file_exists("loop"));
+}
+
 /// Test that copying a directory to itself is disallowed.
 #[test]
 fn test_copy_directory_to_itself_disallowed() {