Merge pull request #755 from wasmx/export-grown-memory

Enforce updated lower limit of exported memory after grow

Author: gumb0

lib/fizzy/instantiate.cpp

@@ -121,9 +121,9 @@ void match_imported_memories(const std::vector<Memory>& module_imported_memories
 
         const auto min = imported_memories[0].limits.min;
         const auto& max = imported_memories[0].limits.max;
-        if (size < memory_pages_to_bytes(min) ||
+        if (size != memory_pages_to_bytes(min) ||
             (max.has_value() && size > memory_pages_to_bytes(*max)))
-            throw instantiate_error{"provided imported memory doesn't fit provided limits"};
+            throw instantiate_error{"provided imported memory size must be equal to its min limit"};
     }
 }
 
@@ -558,7 +558,10 @@ std::optional<ExternalMemory> find_exported_memory(
     if (!find_export(*instance.module, ExternalKind::Memory, name))
         return std::nullopt;
 
-    return ExternalMemory{instance.memory.get(), instance.memory_limits};
+    // Memory lower limit should be updated in case it was grown.
+    const Limits limits{
+        static_cast<uint32_t>(instance.memory->size() / PageSize), instance.memory_limits.max};
+    return ExternalMemory{instance.memory.get(), limits};
 }
 
 }  // namespace fizzy

test/unittests/api_test.cpp

@@ -810,3 +810,77 @@ TEST(api, find_exported_memory_reimport)
     // importing the same table into the module with equal limits, instantiate should succeed
     instantiate(parse(wasm_reimported_memory), {}, {}, {*opt_memory});
 }
+
+TEST(api, find_exported_memory_after_grow)
+{
+    /* wat2wasm
+    (module
+      (memory (export "mem") 1 2)
+      (func (drop (memory.grow (i32.const 1))))
+    )
+    */
+    const auto wasm = from_hex(
+        "0061736d0100000001040160000003020100050401010102070701036d656d02000a09010700410140001a0b");
+
+    auto instance = instantiate(parse(wasm));
+
+    EXPECT_THAT(execute(*instance, 0, {}), Result());
+
+    auto opt_memory = find_exported_memory(*instance, "mem");
+    ASSERT_TRUE(opt_memory);
+    EXPECT_EQ(opt_memory->data->size(), 2 * PageSize);
+    EXPECT_EQ(opt_memory->limits.min, 2);
+    ASSERT_TRUE(opt_memory->limits.max.has_value());
+    EXPECT_EQ(opt_memory->limits.max, 2);
+}
+
+TEST(api, import_grown_memory)
+{
+    /* wat2wasm
+    (module
+      (memory (export "mem") 1)
+      (func (drop (memory.grow (i32.const 1))))
+    )
+    */
+    const auto wasm = from_hex(
+        "0061736d01000000010401600000030201000503010001070701036d656d02000a09010700410140001a0b");
+
+    auto instance = instantiate(parse(wasm));
+
+    EXPECT_THAT(execute(*instance, 0, {}), Result());
+
+    auto memory = find_exported_memory(*instance, "mem");
+    ASSERT_TRUE(memory);
+    EXPECT_EQ(memory->data->size(), 2 * PageSize);
+    EXPECT_EQ(memory->limits.min, 2);
+    ASSERT_FALSE(memory->limits.max.has_value());
+
+    /* wat2wasm
+    (module
+      (memory (export "mem2") (import "m" "mem") 2)
+      (func (drop (memory.grow (i32.const 1))))
+    )
+    */
+    const auto wasm_reexported_mem = from_hex(
+        "0061736d01000000010401600000020a01016d036d656d02000203020100070801046d656d3202000a09010700"
+        "410140001a0b");
+
+    auto instance_reexported_mem = instantiate(parse(wasm_reexported_mem), {}, {}, {*memory});
+
+    EXPECT_THAT(execute(*instance_reexported_mem, 0, {}), Result());
+
+    auto reexported_memory = find_exported_memory(*instance_reexported_mem, "mem2");
+    ASSERT_TRUE(reexported_memory);
+    EXPECT_EQ(reexported_memory->data->size(), 3 * PageSize);
+    EXPECT_EQ(reexported_memory->limits.min, 3);
+    ASSERT_FALSE(reexported_memory->limits.max.has_value());
+
+    /* wat2wasm
+    (module
+      (memory (import "m" "mem2") 2)
+    )
+    */
+    const auto wasm_imported_mem = from_hex("0061736d01000000020b01016d046d656d32020002");
+
+    EXPECT_NO_THROW(instantiate(parse(wasm_imported_mem), {}, {}, {*reexported_memory}));
+}

test/unittests/instantiate_test.cpp

@@ -302,12 +302,12 @@ TEST(instantiate, imported_memory_invalid)
 
     // Allocated less than min
     EXPECT_THROW_MESSAGE(instantiate(*module, {}, {}, {{&memory_empty, {1, 3}}}), instantiate_error,
-        "provided imported memory doesn't fit provided limits");
+        "provided imported memory size must be equal to its min limit");
 
-    // Allocated more than max
-    bytes memory_big(PageSize * 4, 0);
-    EXPECT_THROW_MESSAGE(instantiate(*module, {}, {}, {{&memory_big, {1, 3}}}), instantiate_error,
-        "provided imported memory doesn't fit provided limits");
+    // Allocated more than min but less than max
+    bytes memory_two_pages(PageSize * 2, 0);
+    EXPECT_THROW_MESSAGE(instantiate(*module, {}, {}, {{&memory_two_pages, {1, 3}}}),
+        instantiate_error, "provided imported memory size must be equal to its min limit");
 
     // Provided max exceeds the hard limit
     /* wat2wasm