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feat: Bounds checking for Flatbuf should be enabled in the default build #47

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Merged
CurtHagenlocher merged 1 commit into from
Sep 15, 2025
Merged

feat: Bounds checking for Flatbuf should be enabled in the default build #47

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2 changes: 1 addition & 1 deletion src/Apache.Arrow/Apache.Arrow.csproj
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Expand Up @@ -2,7 +2,7 @@

<PropertyGroup>
<AllowUnsafeBlocks>true</AllowUnsafeBlocks>
<DefineConstants>$(DefineConstants);UNSAFE_BYTEBUFFER;BYTEBUFFER_NO_BOUNDS_CHECK;ENABLE_SPAN_T</DefineConstants>
<DefineConstants>$(DefineConstants);UNSAFE_BYTEBUFFER;ENABLE_SPAN_T</DefineConstants>
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@adamreeve adamreeve Sep 15, 2025

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Just checking we're happy with leaving UNSAFE_BYTEBUFFER enabled? As far as I understand, bounds checks should prevent any invalid reads and this should be safe in theory, but it means bugs in the Flatbuffers implementation (like missing bounds checks) could still cause memory safety issues. It sounds like this can increase performance significantly though so is worth keeping enabled (https://flatbuffers.dev/languages/c_sharp/#conditional-compilation-symbols).

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@CurtHagenlocher CurtHagenlocher Sep 15, 2025

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I didn't try benchmarking without UNSAFE_BYTEBUFFER but I did audit all the code and confirmed that there was only one missing bounds check.


<Description>Apache Arrow is a cross-language development platform for in-memory data. It specifies a standardized language-independent columnar memory format for flat and hierarchical data, organized for efficient analytic operations on modern hardware.</Description>
</PropertyGroup>
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1 change: 1 addition & 0 deletions src/Apache.Arrow/Flatbuf/FlatBuffers/ByteBuffer.cs
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Expand Up @@ -693,6 +693,7 @@ public byte Get(int index)
#if ENABLE_SPAN_T && UNSAFE_BYTEBUFFER
public unsafe string GetStringUTF8(int startPos, int len)
{
AssertOffsetAndLength(startPos, len);
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@adamreeve adamreeve Sep 14, 2025

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For reference, this has been added in the upstream Flatbuffers project but not yet released: google/flatbuffers#8673

So we should make sure if we upgrade the bundled Flatbuffers code we do so after that change is released or add it in manually again. The new test should catch this though.

fixed (byte* buffer = &MemoryMarshal.GetReference(_buffer.ReadOnlySpan.Slice(startPos)))
{
return Encoding.UTF8.GetString(buffer, len);
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4 changes: 2 additions & 2 deletions test/Apache.Arrow.Benchmarks/ArrowWriterBenchmark.cs
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Expand Up @@ -25,10 +25,10 @@ namespace Apache.Arrow.Benchmarks
[MemoryDiagnoser]
public class ArrowWriterBenchmark
{
[Params(10_000, 1_000_000)]
[Params(10_000, 300_000)]
public int BatchLength { get; set; }

//Max column set count is 15 before reaching 2gb limit of memory stream
//Max column set count is 14 before reaching 2gb limit of memory stream
[Params(10, 14)]
public int ColumnSetCount { get; set; }

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36 changes: 35 additions & 1 deletion test/Apache.Arrow.Tests/ArrowStreamReaderTests.cs
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Expand Up @@ -20,6 +20,7 @@
using System.Threading.Tasks;
using Apache.Arrow.Ipc;
using Apache.Arrow.Memory;
using Apache.Arrow.Types;
using Xunit;

namespace Apache.Arrow.Tests
Expand Down Expand Up @@ -280,6 +281,39 @@ public override Task<int> ReadAsync(byte[] buffer, int offset, int length, Cance
}
#endif
}

[Fact]
public unsafe void MalformedColumnNameLength()
{
const int FieldNameLengthOffset = 108;
const int FakeFieldNameLength = 165535;

byte[] buffer;
using (var stream = new MemoryStream())
{
Schema schema = new(
[new Field("index", Int32Type.Default, nullable: false)],
metadata: []);
using (var writer = new ArrowStreamWriter(stream, schema, leaveOpen: true))
{
writer.WriteStart();
writer.WriteEnd();
}
buffer = stream.ToArray();
}

Span<int> length = buffer.AsSpan().Slice(FieldNameLengthOffset, sizeof(int)).CastTo<int>();
Assert.Equal(5, length[0]);
length[0] = FakeFieldNameLength;

Assert.Throws<ArgumentOutOfRangeException>(() =>
{
using (var stream = new MemoryStream(buffer))
using (var reader = new ArrowStreamReader(stream))
{
reader.ReadNextRecordBatch();
}
});
}
}
}

13 changes: 9 additions & 4 deletions test/Apache.Arrow.Tests/TestData.cs
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Expand Up @@ -15,6 +15,7 @@

using System;
using System.Collections.Generic;
using System.Data.SqlTypes;
using System.Linq;
using Apache.Arrow.Arrays;
using Apache.Arrow.Scalars;
Expand Down Expand Up @@ -201,7 +202,8 @@ public void Visit(Decimal32Type type)

for (var i = 0; i < Length; i++)
{
builder.Append((decimal)i / Length);
SqlDecimal value = SqlDecimal.ConvertToPrecScale((decimal)i / Length, type.Precision, type.Scale);
builder.Append((decimal)value);
}

Array = builder.Build();
Expand All @@ -213,7 +215,8 @@ public void Visit(Decimal64Type type)

for (var i = 0; i < Length; i++)
{
builder.Append((decimal)i / Length);
SqlDecimal value = SqlDecimal.ConvertToPrecScale((decimal)i / Length, type.Precision, type.Scale);
builder.Append((decimal)value);
}

Array = builder.Build();
Expand All @@ -225,7 +228,8 @@ public void Visit(Decimal128Type type)

for (var i = 0; i < Length; i++)
{
builder.Append((decimal)i / Length);
SqlDecimal value = SqlDecimal.ConvertToPrecScale((decimal)i / Length, type.Precision, type.Scale);
builder.Append((decimal)value);
}

Array = builder.Build();
Expand All @@ -237,7 +241,8 @@ public void Visit(Decimal256Type type)

for (var i = 0; i < Length; i++)
{
builder.Append((decimal)i / Length);
SqlDecimal value = SqlDecimal.ConvertToPrecScale((decimal)i / Length, type.Precision, type.Scale);
builder.Append((decimal)value);
}

Array = builder.Build();
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