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[vm/ffi] Make overflow checks consistent

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This CL changes the semantics of Pointer.allocate() to not do any range or overflow checks. This is consistent with the truncating behavior that the rest of the FFI has.

Fixes: https://github.com/dart-lang/sdk/issues/37250

Change-Id: Icc2b53e229cd6a2faae99c833ea5df372eb35b74
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/107503
Commit-Queue: Daco Harkes <dacoharkes@google.com>
Reviewed-by: Samir Jindel <sjindel@google.com>
This commit is contained in:
Daco Harkes 2019-06-27 14:26:33 +00:00 committed by commit-bot@chromium.org
parent b4e99fbcd4
commit 04c984ce3f
2 changed files with 22 additions and 17 deletions
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19
runtime/lib/ffi.cc
View file

@ -169,18 +169,6 @@ static void CheckDartAndCTypeCorrespond(const AbstractType& native_type,
// The following functions are runtime checks on arguments.
// Note that expected_from and expected_to are inclusive.
static void CheckRange(const Integer& argument_value,
intptr_t expected_from,
intptr_t expected_to,
const char* argument_name) {
int64_t value = argument_value.AsInt64Value();
if (value < expected_from || expected_to < value) {
Exceptions::ThrowRangeError(argument_name, argument_value, expected_from,
expected_to);
}
}
static const Pointer& AsPointer(const Instance& instance) {
if (!instance.IsPointer()) {
const String& error = String::Handle(String::NewFormatted(
@ -221,11 +209,10 @@ DEFINE_NATIVE_ENTRY(Ffi_allocate, 1, 1) {
GET_NON_NULL_NATIVE_ARGUMENT(Integer, argCount, arguments->NativeArgAt(0));
int64_t count = argCount.AsInt64Value();
classid_t type_cid = type_arg.type_class_id();
int64_t max_count = INTPTR_MAX / compiler::ffi::ElementSizeInBytes(type_cid);
CheckRange(argCount, 1, max_count, "count");
size_t size = compiler::ffi::ElementSizeInBytes(type_cid) * count;
uint64_t memory = reinterpret_cast<uint64_t>(malloc(size));
size_t size = compiler::ffi::ElementSizeInBytes(type_cid) *
count; // Truncates overflow.
size_t memory = reinterpret_cast<size_t>(malloc(size));
if (memory == 0) {
const String& error = String::Handle(String::NewFormatted(
"allocating (%" Pd ") bytes of memory failed", size));

20
tests/ffi/data_test.dart
View file

@ -93,7 +93,25 @@ void testPointerPointerArithmeticSizes() {
}
void testPointerAllocateNonPositive() {
Expect.throws(() => ffi.allocate<ffi.Int8>(count: 0));
// > If size is 0, either a null pointer or a unique pointer that can be
// > successfully passed to free() shall be returned.
// http://pubs.opengroup.org/onlinepubs/009695399/functions/malloc.html
//
// Null pointer throws a Dart exception.
bool returnedNullPointer = false;
ffi.Pointer<ffi.Int8> p;
try {
p = ffi.allocate<ffi.Int8>(count: 0);
} on Exception {
returnedNullPointer = true;
}
if (!returnedNullPointer) {
p.free();
}
// Passing in -1 will be converted into an unsigned integer. So, it will try
// to allocate SIZE_MAX - 1 + 1 bytes. This will fail as it is the max amount
// of addressable memory on the system.
Expect.throws(() => ffi.allocate<ffi.Int8>(count: -1));
}