dd: fix OOM panic with skip=1

Author: oech3

src/uu/dd/src/dd.rs

@@ -185,7 +185,8 @@ impl Num {
 /// Returns the total number of bytes actually read.
 fn read_and_discard<R: Read>(reader: &mut R, n: u64, buf_size: usize) -> io::Result<u64> {
     // todo: consider splice()ing to /dev/null on Linux
-    let mut buf = Vec::with_capacity(buf_size);
+    let mut buf = Vec::new();
+    buf.try_reserve(buf_size.min(n as usize))?; // try_with_capacity is unstable <https://github.com/rust-lang/rust/issues/91913>
     let mut total = 0u64;
     let mut remaining = n;
     while remaining > 0 {

tests/by-util/test_dd.rs

@@ -123,6 +123,15 @@ fn test_out_of_memory() {
         .stderr_contains("memory"); //todo: improve error message at all platforms
 }
 
+#[test]
+fn test_out_of_memory_skip() {
+    new_ucmd!()
+        .arg("bs=1PB")
+        .arg("skip=1")
+        .fails_with_code(1)
+        .stderr_contains("memory");
+}
+
 #[test]
 fn test_stdin_stdout() {
     let input = build_ascii_block(521);