dd: exit when bs/ibs/obs/cbs isn't positive

Author: iburaky2

src/uu/dd/src/parseargs.rs

@@ -182,6 +182,11 @@ impl Parser {
         //     conv=block,unblock,ascii
         //     conv=block conv=unblock conv=ascii
         let block = if let Some(cbs) = self.cbs {
+            // GNU dd exits when cbs is not positive.
+            if cbs <= 0 {
+                return Err(ParseError::InvalidNumber(cbs.to_string()));
+            }
+
             match conversion {
                 Some(Conversion::Ascii) => Some(Block::Unblock(cbs)),
                 Some(_) => Some(Block::Block(cbs)),
@@ -231,6 +236,13 @@ impl Parser {
             Some(bs) => (bs, bs),
         };
 
+        // GNU dd exits when bs, ibs or obs are not positive.
+        for bs in [ibs, obs] {
+            if bs <= 0 {
+                return Err(ParseError::InvalidNumber(bs.to_string()));
+            }
+        }
+
         // Whether to buffer partial output blocks until they are completed.
         //
         // From the GNU `dd` documentation for the `bs=BYTES` option: