Fix issue with syncing a Decimal128 with big significand (#5740)

* Will transfer all bits to server
* Update Baas docker image version

CHANGELOG.md

@@ -19,6 +19,7 @@
 * Fix all UBSan failures hit by tests. It is unclear if any of these manifested as visible bugs. ([PR #5665](https://github.com/realm/realm-core/pull/5665))
 * Fix sorting order for `realm_query_find_first` in the C API.([#5720](https://github.com/realm/realm-core/issues/5720))
 * Upload completion callbacks may have called before the download message that completed them was fully integrated. ([#4865](https://github.com/realm/realm-core/issues/4865)).
+* Syncing of a Decimal128 with big significand could result in a crash. ([#5728](https://github.com/realm/realm-core/issues/5728))
 
 
 ### Breaking changes

dependencies.list

@@ -1,4 +1,4 @@
 PACKAGE_NAME=realm-core
 VERSION=12.5.1
 OPENSSL_VERSION=1.1.1n
-MDBREALM_TEST_SERVER_TAG=2022-08-10
+MDBREALM_TEST_SERVER_TAG=2022-09-01

evergreen/install_baas.sh

@@ -58,7 +58,7 @@ case $(uname -s) in
             DISTRO_VERSION_MAJOR="$(cut -d. -f1 <<< "$DISTRO_VERSION" )"
         fi
         case $DISTRO_NAME in
-            ubuntu)
+            ubuntu | linuxmint)
                 MONGODB_DOWNLOAD_URL="http://downloads.10gen.com/linux/mongodb-linux-$(uname -m)-enterprise-ubuntu${DISTRO_VERSION_MAJOR}04-5.0.3.tgz"
                 STITCH_ASSISTED_AGG_LIB_URL="https://stitch-artifacts.s3.amazonaws.com/stitch-mongo-libs/stitch_mongo_libs_ubuntu2004_x86_64_0bdbed3d42ea136e166b3aad8f6fd09f336b1668_22_03_29_14_36_02/libmongo-ubuntu2004-x86_64.so"
                 STITCH_SUPPORT_LIB_URL="https://mciuploads.s3.amazonaws.com/mongodb-mongo-v4.4/stitch-support/ubuntu2004/58971da1ef93435a9f62bf4708a81713def6e88c/stitch-support-4.4.9-73-g58971da.tgz"

src/realm/sync/changeset_encoder.cpp

@@ -389,10 +389,12 @@ void ChangesetEncoder::append_value(Decimal128 id)
     int exp;
     bool sign;
     id.unpack(cx, exp, sign);
-    char buffer[16];
+    constexpr int max_bytes = 17; // 113 bits / 7
+    char buffer[max_bytes];
     _impl::Bid128 tmp;
     memcpy(&tmp, &cx, sizeof(Decimal128::Bid128));
     auto n = _impl::encode_int(buffer, tmp);
+    REALM_ASSERT(n <= max_bytes);
     append_bytes(buffer, n);
     append_value(int64_t(exp));
     append_value(sign);

src/realm/sync/noinst/integer_codec.hpp

@@ -176,7 +176,7 @@ bool decode_int(I& input, _impl::Bid128& value) noexcept
 {
     uint64_t value_0 = 0;
     uint64_t value_1 = 0;
-    constexpr int max_bytes = 16; // 112 bits / 7
+    constexpr int max_bytes = 17; // 113 bits / 7
 
     int i = 0;
     for (;;) {

test/object-store/sync/app.cpp

@@ -1586,6 +1586,55 @@ TEST_CASE("app: mixed lists with object links", "[sync][app]") {
     }
 }
 
+TEST_CASE("app: roundtrip values", "[sync][app]") {
+    std::string base_url = get_base_url();
+    const std::string valid_pk_name = "_id";
+    REQUIRE(!base_url.empty());
+
+    Schema schema{
+        {"TopLevel",
+         {
+             {valid_pk_name, PropertyType::ObjectId, Property::IsPrimary{true}},
+             {"decimal", PropertyType::Decimal | PropertyType::Nullable},
+         }},
+    };
+
+    auto server_app_config = minimal_app_config(base_url, "roundtrip_values", schema);
+    auto app_session = create_app(server_app_config);
+    auto partition = random_string(100);
+
+    Decimal128 large_significand = Decimal128(70) / Decimal128(1.09);
+    auto obj_id = ObjectId::gen();
+    {
+        TestAppSession test_session(app_session, nullptr, DeleteApp{false});
+        SyncTestFile config(test_session.app(), partition, schema);
+        auto realm = Realm::get_shared_realm(config);
+
+        CppContext c(realm);
+        realm->begin_transaction();
+        Object::create(c, realm, "TopLevel",
+                       util::Any(AnyDict{
+                           {valid_pk_name, obj_id},
+                           {"decimal", large_significand},
+                       }),
+                       CreatePolicy::ForceCreate);
+        realm->commit_transaction();
+        CHECK(!wait_for_upload(*realm, std::chrono::seconds(600)));
+    }
+
+    {
+        TestAppSession test_session(app_session);
+        SyncTestFile config(test_session.app(), partition, schema);
+        auto realm = Realm::get_shared_realm(config);
+
+        CHECK(!wait_for_download(*realm));
+        CppContext c(realm);
+        auto obj = Object::get_for_primary_key(c, realm, "TopLevel", util::Any{obj_id});
+        auto val = obj.get_column_value<Decimal128>("decimal");
+        CHECK(val == large_significand);
+    }
+}
+
 TEST_CASE("app: upgrade from local to synced realm", "[sync][app]") {
     std::string base_url = get_base_url();
     const std::string valid_pk_name = "_id";

test/test_instruction_replication.cpp

@@ -215,17 +215,20 @@ TEST(InstructionReplication_CreateObjectObjectIdPK)
     Decimal128 large_w0_zero(uint64_t(0x1234500000000000));
     large_w0_zero *= Decimal128(0x1000000);
     large_w0_zero += Decimal128(0x23);
+    Decimal128 large_significand = Decimal128(70) / Decimal128(1.09);
     Fixture fixture{test_context};
     ObjKey key;
     ObjKey key2;
     ObjKey key3;
+    ObjKey key4;
     {
         WriteTransaction wt{fixture.sg_1};
         TableRef foo = wt.get_group().add_table_with_primary_key("class_foo", type_ObjectId, "_id", false);
         auto col_dec = foo->add_column(type_Decimal, "cost");
         key = foo->create_object_with_primary_key(id).set(col_dec, cost).get_key();
         key2 = foo->create_object_with_primary_key(ObjectId::gen()).set(col_dec, large).get_key();
         key3 = foo->create_object_with_primary_key(ObjectId::gen()).set(col_dec, large_w0_zero).get_key();
+        key4 = foo->create_object_with_primary_key(ObjectId::gen()).set(col_dec, large_significand).get_key();
         wt.commit();
     }
     fixture.replay_transactions();
@@ -234,7 +237,7 @@ TEST(InstructionReplication_CreateObjectObjectIdPK)
         ReadTransaction rt{fixture.sg_2};
         CHECK(rt.has_table("class_foo"));
         ConstTableRef foo = rt.get_table("class_foo");
-        CHECK_EQUAL(foo->size(), 3);
+        CHECK_EQUAL(foo->size(), 4);
         ColKey col_ndx = foo->get_column_key("_id");
         ColKey col_dec = foo->get_column_key("cost");
         auto obj = foo->get_object(key);
@@ -244,6 +247,8 @@ TEST(InstructionReplication_CreateObjectObjectIdPK)
         CHECK_EQUAL(obj.get<Decimal128>(col_dec), large);
         obj = foo->get_object(key3);
         CHECK_EQUAL(obj.get<Decimal128>(col_dec), large_w0_zero);
+        obj = foo->get_object(key4);
+        CHECK_EQUAL(obj.get<Decimal128>(col_dec), large_significand);
     }
 }