Fix DeflateStream retaining stale buffer reference after write failure mid-operation

[alinpahontu2912]

Fixes #132393

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[Copilot]

Pull request overview

This PR hardens System.IO.Compression’s deflate implementation against mid-operation failures by ensuring the zlib deflater/inflater won’t retain (and later read from) stale caller-provided input buffers after an exception propagates (e.g., write failure/cancellation), including during subsequent Dispose/flush paths.

Changes:

• Add UnsetInput() helpers to Deflater and Inflater to discard any unconsumed input and release pinned references.
• Ensure DeflateStream clears engine input on exceptions in deflate-output write loops and in CopyTo decompression forwarding.
• Add regression tests intended to validate that stale input isn’t retained after failure paths.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/libraries/System.IO.Compression/src/System/IO/Compression/DeflateZLib/Inflater.cs	Adds UnsetInput() to drop unconsumed pinned input for inflate paths.
src/libraries/System.IO.Compression/src/System/IO/Compression/DeflateZLib/DeflateStream.cs	Clears stale input on exceptional paths during compress output writes and CopyTo decompression forwarding.
src/libraries/System.IO.Compression/src/System/IO/Compression/DeflateZLib/Deflater.cs	Adds UnsetInput() to drop unconsumed pinned input for deflate paths.
src/libraries/Common/tests/System/IO/Compression/CompressionStreamUnitTestBase.cs	Adds regression tests exercising exception mid-operation behavior for compression and decompression.

[iremyux]

The copilot comment looks legit, otherwise LGTM

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

Suppressed comments (2)

src/libraries/System.IO.Compression/src/System/IO/Compression/DeflateZLib/Inflater.cs:287

• The XML doc comment has a grammatical typo: 'may since have' should be 'may have since' for correct wording.

        /// the inflater doesn't retain a dangling reference to a buffer the caller may since have reused or freed.

src/libraries/Common/tests/System/IO/Compression/CompressionStreamUnitTestBase.cs:172

• This reflection lookup restricts to BindingFlags.Public, but NeedsInput on the internal engine types may be non-public. If so, GetMethod(...) returns null and the null-forgiving operator will cause a test failure. Use BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance (or otherwise handle a null MethodInfo) to make the test resilient to visibility.

            MethodInfo needsInputMethod = engine.GetType().GetMethod("NeedsInput", BindingFlags.Public | BindingFlags.Instance)!;
            return (bool)needsInputMethod.Invoke(engine, null)!;