cp: harden sparse_copy against 32-bit panic and EOF hang

src/uu/cp/src/platform/linux.rs

@@ -167,23 +167,28 @@ where
     let mut src_file = open_source(source, nofollow)?;
     let dst_file = create_dest_restrictive(dest, false)?;
 
-    let size: usize = src_file.metadata()?.size().try_into().unwrap();
-    ftruncate(&dst_file, size.try_into().unwrap())?;
+    let size = src_file.metadata()?.size();
+    ftruncate(&dst_file, size)?;
 
-    let blksize = dst_file.metadata()?.blksize();
-    let mut buf: Vec<u8> = vec![0; blksize.try_into().unwrap()];
-    let mut current_offset: usize = 0;
+    let blksize = dst_file.metadata()?.blksize() as usize;
+    let mut buf: Vec<u8> = vec![0; blksize];
+    let mut current_offset: u64 = 0;
 
     // TODO Perhaps we can employ the "fiemap ioctl" API to get the
     // file extent mappings:
     // https://www.kernel.org/doc/html/latest/filesystems/fiemap.html
     while current_offset < size {
         let this_read = src_file.read(&mut buf)?;
+        if this_read == 0 {
+            // The source shrank (e.g. truncated concurrently) before we reached
+            // its reported size; stop instead of looping forever on EOF reads.
+            break;
+        }
         let buf = &buf[..this_read];
         if buf.iter().any(|&x| x != 0) {
-            dst_file.write_all_at(buf, current_offset.try_into().unwrap())?;
+            dst_file.write_all_at(buf, current_offset)?;
         }
-        current_offset += this_read;
+        current_offset += this_read as u64;
     }
     Ok(())
 }

tests/by-util/test_cp.rs

@@ -3942,6 +3942,26 @@ fn test_reflink_never_sparse_always() {
     assert_eq!(dest_metadata.len(), 1024 * 1024);
 }
 
+#[cfg(any(target_os = "linux", target_os = "android"))]
+#[test]
+fn test_reflink_never_sparse_always_data_is_copied() {
+    // `--reflink=never --sparse=always` goes through the read-loop sparse copy.
+    // A file with data spread across several blocks must be copied byte-for-byte.
+    let (at, mut ucmd) = at_and_ucmd!();
+
+    let mut buf = vec![0u8; 4096 * 4 + 7];
+    for i in [0, buf.len() / 2, buf.len() - 1] {
+        buf[i] = b'x';
+    }
+    at.write_bytes("src", &buf);
+
+    ucmd.args(&["--reflink=never", "--sparse=always", "src", "dest"])
+        .succeeds()
+        .no_output();
+
+    assert_eq!(at.read_bytes("dest"), buf);
+}
+
 /// Test for preserving attributes of a hard link in a directory.
 #[test]
 #[cfg(not(any(target_os = "android", target_os = "openbsd")))]