streams: Add stream position validation in BufferedFile::AdvanceStream #31839

1. 
   crStiv commented at 0:41 am on February 11, 2025: none

   Description: Add safety check in BufferedFile::AdvanceStream to prevent potential integer overflow when calculating bytes_until_source_pos. This ensures that m_read_pos never exceeds nSrcPos, which could lead to undefined behavior.

   The change:

   • Adds validation before calculating (nSrcPos - m_read_pos)
   • Throws std::ios_base::failure if invalid state is detected
2. Update streams.h a88db6b66d
3. 
   DrahtBot commented at 0:41 am on February 11, 2025: contributor

   The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

   Code Coverage & Benchmarks

   For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/31839.

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4. 
   maflcko commented at 7:06 am on February 11, 2025: member

   The prior assert with the exact same check covers this. This is adding dead code.

   Is this AI generated?

5. maflcko closed this on Feb 11, 2025

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6. 
   mzumsande commented at 4:57 pm on February 11, 2025: contributor

   The prior assert with the exact same check covers this. This is adding dead code.

   Fill() may be called in between, which can change nSrcPos - but it can only increase it, so yes, still dead code.

Contributors
crStiv DrahtBot maflcko mzumsande