From 1b26cd8a12f2635678638d0bbb427f5c5a49bc09 Mon Sep 17 00:00:00 2001
From: weili <541602953@qq.com>
Date: Fri, 5 Jun 2026 04:17:51 +0000
Subject: [PATCH] split: reject a zero chunk count for -n l/N and r/N

`split -n l/0` and `split -n r/0` aborted with a divide-by-zero panic
(`num_bytes / num_chunks` in `n_chunks_by_line` and `i % num_chunks` in
`n_chunks_by_line_round_robin`). `NumberType::from` validated `N > 0` for
the bare `N` / `K/N` forms but not for the `l/N` and `r/N` forms, so a
zero count reached the chunk arithmetic.

Reject `num_chunks == 0` in those two branches, returning
`NumberTypeError::NumberOfChunks` like the bare-`N` form, which matches
GNU (`split: invalid number of chunks: '0'`, exit 1) and validates up
front rather than crashing while reading input.
---
 src/uu/split/src/strategy.rs | 18 ++++++++++++++++++
 tests/by-util/test_split.rs  | 16 ++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/src/uu/split/src/strategy.rs b/src/uu/split/src/strategy.rs
index 6d567637d07..e35f62d3a7f 100644
--- a/src/uu/split/src/strategy.rs
+++ b/src/uu/split/src/strategy.rs
@@ -144,6 +144,9 @@ impl NumberType {
             (Some("l"), Some(n_str), None, None) => {
                 let num_chunks = parse_size_u64(n_str)
                     .map_err(|_| NumberTypeError::NumberOfChunks(n_str.to_string()))?;
+                if num_chunks == 0 {
+                    return Err(NumberTypeError::NumberOfChunks(n_str.to_string()));
+                }
                 Ok(Self::Lines(num_chunks))
             }
             (Some("l"), Some(k_str), Some(n_str), None) => {
@@ -159,6 +162,9 @@ impl NumberType {
             (Some("r"), Some(n_str), None, None) => {
                 let num_chunks = parse_size_u64(n_str)
                     .map_err(|_| NumberTypeError::NumberOfChunks(n_str.to_string()))?;
+                if num_chunks == 0 {
+                    return Err(NumberTypeError::NumberOfChunks(n_str.to_string()));
+                }
                 Ok(Self::RoundRobin(num_chunks))
             }
             (Some("r"), Some(k_str), Some(n_str), None) => {
@@ -345,6 +351,18 @@ mod tests {
             NumberType::from("r/xyz").unwrap_err(),
             NumberTypeError::NumberOfChunks("xyz".to_string())
         );
+        assert_eq!(
+            NumberType::from("0").unwrap_err(),
+            NumberTypeError::NumberOfChunks("0".to_string())
+        );
+        assert_eq!(
+            NumberType::from("l/0").unwrap_err(),
+            NumberTypeError::NumberOfChunks("0".to_string())
+        );
+        assert_eq!(
+            NumberType::from("r/0").unwrap_err(),
+            NumberTypeError::NumberOfChunks("0".to_string())
+        );
         assert_eq!(
             NumberType::from("r/123/xyz").unwrap_err(),
             NumberTypeError::NumberOfChunks("xyz".to_string())
diff --git a/tests/by-util/test_split.rs b/tests/by-util/test_split.rs
index a5d67402396..8b598c49e92 100644
--- a/tests/by-util/test_split.rs
+++ b/tests/by-util/test_split.rs
@@ -633,6 +633,22 @@ fn test_split_obs_lines_as_other_option_value() {
         .stderr_contains("split: invalid number of chunks: '-e200'\n");
 }
 
+#[test]
+fn test_split_chunks_by_line_or_round_robin_zero_chunks() {
+    let scene = TestScenario::new(util_name!());
+    scene.fixtures.write("file", "a\nb\nc\nd\n");
+    scene
+        .ucmd()
+        .args(&["-n", "l/0", "file"])
+        .fails_with_code(1)
+        .stderr_only("split: invalid number of chunks: '0'\n");
+    scene
+        .ucmd()
+        .args(&["-n", "r/0", "file"])
+        .fails_with_code(1)
+        .stderr_only("split: invalid number of chunks: '0'\n");
+}
+
 /// Test for using more than one obsolete lines option (standalone)
 /// last one wins
 #[test]