[DiagnosticServer] Impove ipc message parsing resiliency

[mdh1418]

While investigating for a way to check whether arbitrary .NET processes support emitting userevents, the idea of probing for DS_IPC_E_UNKNOWN_COMMAND 0x80131385 with an empty payload uncovered a problem with truncated payloads. Additionally, there were two other places to improve the resiliency of IPC protocol parsing.

[Copilot]

Pull request overview

This PR improves the resiliency of IPC message parsing in the Diagnostic Server by addressing issues with truncated payloads. The changes add defensive checks to prevent buffer underruns and ensure proper data alignment when parsing UTF-16 strings.

Key Changes:

• Added alignment validation for UTF-16 string parsing to ensure buffer pointers are properly aligned
• Replaced an ineffective underflow assertion with both a clearer assertion and runtime validation in ds_ipc_message_try_parse_value
• Fixed comparison logic in attach_profiler_command_try_parse_payload to correctly validate sufficient buffer space

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/native/eventpipe/ds-protocol.c	Adds buffer alignment check for UTF-16 parsing and improves buffer length validation with runtime check
src/native/eventpipe/ds-profiler-protocol.c	Corrects buffer size validation from <= to >= to ensure adequate remaining buffer