ARROW-4501: Fix out-of-bounds read in DoubleCrcHash

Author: TocarIP

cpp/src/arrow/util/hash-util.h

@@ -133,13 +133,13 @@ class HashUtil {
     }
     switch (nbytes) {
       case 3:
-        h1 = HW_crc32_u8(h1, p[3]);
+        h1 = HW_crc32_u8(h1, p[2]);
         // fallthrough
       case 2:
-        h2 = HW_crc32_u8(h2, p[2]);
+        h2 = HW_crc32_u8(h2, p[1]);
         // fallthrough
       case 1:
-        h1 = HW_crc32_u8(h1, p[1]);
+        h1 = HW_crc32_u8(h1, p[0]);
         // fallthrough
       case 0:
         break;

cpp/src/arrow/util/hashing-test.cc

@@ -126,6 +126,25 @@ TEST(HashingQuality, Strings) {
             0.96 * static_cast<double>(2 * values.size()));
 }
 
+TEST(HashingBounds, Strings) {
+  std::vector<size_t> sizes({1, 2, 3, 4, 5, 7, 8, 9, 15, 16, 17, 18, 19, 20, 21});
+  for (const auto s : sizes) {
+    std::string str;
+    for (size_t i = 0; i < s; i++) {
+      str.push_back(static_cast<char>(i));
+    }
+    hash_t h = ComputeStringHash<1>(str.c_str(), str.size());
+    int different = 0;
+    for (char i = 0; i < 120; i++) {
+      str[str.size() - 1] = i;
+      if (ComputeStringHash<1>(str.c_str(), str.size()) != h) {
+        different++;
+      }
+    }
+    ASSERT_GE(different, 118);
+  }
+}
+
 TEST(ScalarMemoTable, Int64) {
   const int64_t A = 1234, B = 0, C = -98765321, D = 12345678901234LL, E = -1, F = 1,
                 G = 9223372036854775807LL, H = -9223372036854775807LL - 1;