adamreeve commented on code in PR #406: URL: https://github.com/apache/arrow-dotnet/pull/406#discussion_r3799271652
########## test/Apache.Arrow.Tests/PoisonMemoryAllocator.cs: ########## @@ -0,0 +1,69 @@ +// Licensed to the Apache Software Foundation (ASF) under one or more +// contributor license agreements. See the NOTICE file distributed with +// this work for additional information regarding copyright ownership. +// The ASF licenses this file to You under the Apache License, Version 2.0 +// (the "License"); you may not use this file except in compliance with +// the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +using System; +using System.Buffers; +using Apache.Arrow.Memory; + +namespace Apache.Arrow.Tests +{ + public class PoisonMemoryAllocator : MemoryAllocator + { + public PoisonMemoryAllocator(int alignment = DefaultAlignment) : base(alignment) + { + } + + protected override IMemoryOwner<byte> AllocateInternal(int length, out int bytesAllocated) + { + var innerOwner = NativeMemoryAllocator.Default.Value.Allocate(length); + bytesAllocated = length; + return new PoisonMemoryOwner(innerOwner); + } + + private sealed class PoisonMemoryOwner : IMemoryOwner<byte> + { + private readonly IMemoryOwner<byte> _inner; + private bool _disposed; + + public PoisonMemoryOwner(IMemoryOwner<byte> inner) + { + _inner = inner ?? throw new ArgumentNullException(nameof(inner)); + } + + public Memory<byte> Memory + { + get + { + if (_disposed) + { + throw new ObjectDisposedException(nameof(PoisonMemoryOwner)); + } + return _inner.Memory; + } + } + + public void Dispose() + { + if (_disposed) + { + return; + } + _disposed = true; + _inner.Memory.Span.Fill(0xFF); + _inner.Dispose(); Review Comment: Won't this end up calling `Marshal.FreeHGlobal` on the allocated memory: https://github.com/apache/arrow-dotnet/blob/c42689e99046fe5709492f2fcdd9ceafa937bfad/src/Apache.Arrow/Memory/NativeMemoryAllocator.cs#L57 So reading from the Span above reads from freed memory and is not safe. You might want to instead keep the inner `IMemoryOwner` undisposed and alive so you can test the poisoning safely? ########## test/Apache.Arrow.Tests/ArrowBufferTests.cs: ########## @@ -111,6 +113,26 @@ public void TestExternalMemoryWrappedAsArrowBuffer() Assert.Equal(10, buffer.Span.CastTo<int>()[2]); } + [Fact] + public void TestNativeMemoryManagerUseAfterFree() + { + var allocator = new PoisonMemoryAllocator(); + // Allocate using the Builder pattern + var builder = new ArrowBuffer.Builder<byte>(100000); + builder.Append(new byte[100000]); + ArrowBuffer buffer = builder.Build(allocator); + + // Extract the unmanaged Span + ReadOnlySpan<byte> span = buffer.Span; + + // Dispose the buffer to trigger memory poisoning and release + buffer.Dispose(); + + // This will now fail because span[50000] is poisoned with 0xFF after free instead of 0! Review Comment: This comment seems wrong to me. Won't the assertion pass because the value is 0xFF due to the poisoning? ```suggestion // span[50000] is poisoned with 0xFF after free, it's not the initial 0 value ``` -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
