split: do not overflow on -n l/K when K is larger than the byte count

src/uu/split/src/split.rs

@@ -1137,7 +1137,9 @@ fn n_chunks_by_line(
         let num_line_bytes = bytes.len() as u64;
         num_bytes_written += num_line_bytes;
         let mut skipped = -1;
-        while num_bytes_should_be_written <= num_bytes_written {
+        // Stop at the last chunk: with more chunks than bytes the increment is 0,
+        // so without this bound the loop spins until chunk_number/skipped overflow.
+        while num_bytes_should_be_written <= num_bytes_written && chunk_number < num_chunks {
             num_bytes_should_be_written +=
                 chunk_size_base + (chunk_size_reminder > chunk_number) as u64;
             chunk_number += 1;

tests/by-util/test_split.rs

@@ -253,6 +253,19 @@ fn test_split_num_prefixed_chunks_by_lines() {
     assert_eq!(glob.collate(), at.read_bytes(name));
 }
 
+#[test]
+fn test_number_of_chunks_by_line_more_chunks_than_bytes() {
+    // More chunks than bytes must not overflow; the trailing chunks are empty.
+    let (at, mut ucmd) = at_and_ucmd!();
+    at.write("in", "ab");
+    ucmd.args(&["-n", "l/5", "in"]).succeeds().no_stderr();
+    assert_eq!(at.read("xaa"), "ab");
+    for name in ["xab", "xac", "xad", "xae"] {
+        assert_eq!(at.read(name), "");
+    }
+    assert!(!at.file_exists("xaf"));
+}
+
 #[test]
 fn test_split_str_prefixed_chunks_by_lines() {
     let (at, mut ucmd) = at_and_ucmd!();