dd: don't panic on huge count/skip/seek operands

src/uu/dd/src/dd.rs

@@ -161,7 +161,10 @@ impl Num {
 
     fn to_bytes(self, block_size: u64) -> u64 {
         match self {
-            Self::Blocks(n) => n * block_size,
+            // Saturate on overflow: a byte count above `u64::MAX` is far beyond
+            // the `i64::MAX` (intmax_t) limit that callers enforce, so clamping
+            // here turns a would-be panic into that clean "too large" error.
+            Self::Blocks(n) => n.saturating_mul(block_size),
             Self::Bytes(n) => n,
         }
     }

src/uu/dd/src/parseargs.rs

@@ -266,6 +266,16 @@ impl Parser {
         }
 
         let count = self.count.map(|c| c.force_bytes_if(self.iflag.count_bytes));
+        // GNU coreutils has a limit of i64 (intmax_t)
+        if let Some(count) = count {
+            let count_bytes = count.to_bytes(ibs as u64);
+            if count_bytes > i64::MAX as u64 {
+                return Err(ParseError::InvalidNumberWithErrMsg(
+                    format!("{count_bytes}"),
+                    "Value too large for defined data type".to_string(),
+                ));
+            }
+        }
 
         Ok(Settings {
             skip,

tests/by-util/test_dd.rs

@@ -132,6 +132,26 @@ fn test_out_of_memory_skip() {
         .stderr_contains("memory");
 }
 
+#[test]
+fn test_large_numeric_operands_do_not_panic() {
+    // Regression test for GH #12843, #12845, #12846, #12848: a huge
+    // count/skip/seek/iseek/oseek operand overflowed an internal multiplication
+    // and panicked instead of reporting a clean "too large" error.
+    for operand in [
+        "count=177817277272177278",
+        "skip=99999999999999999999",
+        "seek=99999999999999999999",
+        "iseek=166727721627616621762772",
+        "oseek=166727721627616621762772",
+    ] {
+        new_ucmd!()
+            .arg(operand)
+            .pipe_in("")
+            .fails_with_code(1)
+            .stderr_contains("Value too large for defined data type");
+    }
+}
+
 #[test]
 fn test_stdin_stdout() {
     let input = build_ascii_block(521);