fix: bitops_family crash fixed (#4989)

fixed: #4988

Author: vyavdoshenko

src/server/bitops_family.cc

@@ -728,17 +728,25 @@ ResultType Get::ApplyTo(Overflow ov, const string* bitfield) {
   const size_t offset = attr_.offset;
   auto last_byte_offset = GetByteIndex(attr_.offset + attr_.encoding_bit_size - 1);
 
+  if (GetByteIndex(offset) >= total_bytes) {
+    return 0;
+  }
+
+  const string* result_str = bitfield;
+  string buff;
   uint32_t lsb = attr_.offset + attr_.encoding_bit_size - 1;
-  if (last_byte_offset > total_bytes) {
-    return {};
+  if (last_byte_offset >= total_bytes) {
+    buff = *bitfield;
+    buff.resize(last_byte_offset + 1, 0);
+    result_str = &buff;
   }
 
   const bool is_negative =
       CheckBitStatus(GetByteValue(bytes, offset), GetNormalizedBitIndex(offset));
 
   int64_t result = 0;
   for (size_t i = 0; i < attr_.encoding_bit_size; ++i) {
-    uint8_t byte{GetByteValue(bytes, lsb)};
+    uint8_t byte{GetByteValue(*result_str, lsb)};
     int32_t index = GetNormalizedBitIndex(lsb);
     int64_t old_bit = CheckBitStatus(byte, index);
     result |= old_bit << i;
@@ -830,10 +838,11 @@ ResultType IncrBy::ApplyTo(Overflow ov, string* bitfield) {
   string& bytes = *bitfield;
   Get get(attr_);
   auto res = get.ApplyTo(ov, &bytes);
+  const int32_t total_bytes = static_cast<int32_t>(bytes.size());
+  auto last_byte_offset = GetByteIndex(attr_.offset + attr_.encoding_bit_size - 1);
 
-  if (!res) {
-    Set set(attr_, incr_value_);
-    return set.ApplyTo(ov, &bytes);
+  if (last_byte_offset >= total_bytes) {
+    bytes.resize(last_byte_offset + 1, 0);
   }
 
   if (!HandleOverflow(ov, &*res)) {

src/server/bitops_family_test.cc

@@ -805,4 +805,21 @@ TEST_F(BitOpsFamilyTest, BitFieldOperations) {
   ASSERT_THAT(Run({"bitfield", "foo", "get", "u1", "15"}), IntArg(1));
 }
 
+TEST_F(BitOpsFamilyTest, BitFieldLargeOffset) {
+  Run({"set", "foo", "bar"});
+
+  auto resp = Run({"bitfield", "foo", "get", "u32", "0", "overflow", "fail", "incrby", "u32", "0",
+                   "4294967295"});
+  EXPECT_THAT(resp, RespArray(ElementsAre(IntArg(1650553344), ArgType(RespExpr::NIL))));
+
+  resp = Run({"strlen", "foo"});
+  EXPECT_THAT(resp, 4);
+
+  resp = Run({"get", "foo"});
+  EXPECT_THAT(ToSV(resp.GetBuf()), Eq(std::string_view("bar\0", 4)));
+
+  resp = Run({"bitfield", "foo", "get", "u32", "4294967295"});
+  EXPECT_THAT(resp, 0);
+}
+
 }  // end of namespace dfly