Validate maximum thread count

CHANGELOG.md

@@ -5,6 +5,8 @@
 - Add `--exact` option to match the entire filename exactly (literal, non-substring).
 
 ## Bugfixes
+- Reject `--threads` values above 64 instead of panicking during resource
+  allocation, see #2078 (@Sushanth012).
 - Sanitize control characters and bidirectional override characters in filenames
   when output goes to a terminal, to prevent terminal escape-sequence injection.
   Also reject a placeholder as the executable for `--exec-batch`, while still

src/cli.rs

@@ -18,6 +18,8 @@ use crate::filesystem;
 use crate::filter::OwnerFilter;
 use crate::filter::SizeFilter;
 
+const MAX_NUM_THREADS: usize = 64;
+
 #[derive(Parser)]
 #[command(
     name = "fd",
@@ -553,7 +555,7 @@ pub struct Opts {
 
     /// Set number of threads to use for searching & executing (default: number
     /// of available CPU cores)
-    #[arg(long, short = 'j', value_name = "num", hide_short_help = true, value_parser = str::parse::<NonZeroUsize>)]
+    #[arg(long, short = 'j', value_name = "num", hide_short_help = true, value_parser = parse_num_threads)]
     pub threads: Option<NonZeroUsize>,
 
     /// Milliseconds to buffer before streaming search results to console
@@ -792,13 +794,25 @@ fn default_num_threads() -> NonZeroUsize {
     let fallback = NonZeroUsize::MIN;
     // To limit startup overhead on massively parallel machines, don't use more
     // than 64 threads.
-    let limit = NonZeroUsize::new(64).unwrap();
+    let limit = NonZeroUsize::new(MAX_NUM_THREADS).unwrap();
 
     std::thread::available_parallelism()
         .unwrap_or(fallback)
         .min(limit)
 }
 
+fn parse_num_threads(arg: &str) -> Result<NonZeroUsize, String> {
+    let threads = arg
+        .parse::<NonZeroUsize>()
+        .map_err(|error| error.to_string())?;
+    if threads.get() > MAX_NUM_THREADS {
+        return Err(format!(
+            "the number of threads cannot exceed {MAX_NUM_THREADS}"
+        ));
+    }
+    Ok(threads)
+}
+
 #[derive(Copy, Clone, PartialEq, Eq, ValueEnum)]
 pub enum FileType {
     #[value(alias = "f")]
@@ -969,3 +983,15 @@ fn ensure_current_directory_exists(current_directory: &Path) -> anyhow::Result<(
         ))
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::parse_num_threads;
+
+    #[test]
+    fn number_of_threads_is_bounded() {
+        assert_eq!(parse_num_threads("64").unwrap().get(), 64);
+        assert!(parse_num_threads("65").is_err());
+        assert!(parse_num_threads("9223372036854775807").is_err());
+    }
+}

tests/tests.rs

@@ -2659,6 +2659,8 @@ fn test_number_parsing_errors() {
     te.assert_failure(&["--threads=a"]);
     te.assert_failure(&["-j", ""]);
     te.assert_failure(&["--threads=0"]);
+    te.assert_failure(&["--threads=65"]);
+    te.assert_failure(&["--threads=9223372036854775807"]);
 
     te.assert_failure(&["--min-depth=a"]);
     te.assert_failure(&["--mindepth=a"]);