Fix crash when relocation section is malformed

[dthaler]

Found by a fuzzer

Summary by CodeRabbit

• New Features
  • Enhanced error handling for ELF file processing, improving robustness and reliability.
• Bug Fixes
  • Added checks to prevent out-of-bounds access and handle zero-size subprograms, reducing potential runtime errors.
• Refactor
  • Updated function signatures for improved clarity and usability.

[coderabbitai]

Walkthrough

The pull request introduces modifications to the src/asm_files.cpp file, focusing on enhancing error handling and control flow in ELF file processing. Key changes include new checks for valid section indices in the append_subprograms function, error handling for zero-size subprograms in read_subprogram, and comprehensive error checks in the read_elf function for symbol sections and entry sizes. Additionally, the function signature for read_elf has been updated to accept an input stream instead of a file path.

Changes

File	Change Summary
src/asm_files.cpp	- Enhanced error handling in append_subprograms to check section_index validity.
	- Added error check in read_subprogram for zero-size subprograms, throwing UnmarshalError.
	- Modified read_elf to include checks for the symbol section and entry size validation, throwing UnmarshalError for discrepancies.
	- Updated function signature of read_elf to accept std::istream& input_stream instead of const string& path.

Possibly related PRs

• Support bpf2bpf calls from ELF files #693: Modifications to src/asm_files.cpp enhance handling of subprograms and relocations, relating to error handling improvements.
• Cleanup asm_files.cpp #694: Updates to src/asm_files.cpp, specifically in append_subprogram, are directly relevant to the main PR's error handling changes.
• Use gsl::narrow in asm files #710: Involves changes to src/asm_files.cpp, particularly in read_elf, which is also modified in the main PR for better error handling.
• Put bpf2bpf caller in a named section #714: Modifications in src/asm_files.cpp focus on function relocations, aligning with the main PR's emphasis on error handling in ELF processing.

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📥 Commits

Reviewing files that changed from the base of the PR and between b245031 and 49e82a1.

📒 Files selected for processing (1)

• src/asm_files.cpp (1 hunks)

🔇 Additional comments (1)

src/asm_files.cpp (1)

248-251: Bounds check correctly implemented.

The added check ensures section_index is within the valid range before accessing reader.sections, preventing out-of-bounds access.

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[coderabbitai]

Actionable comments posted: 1

📜 Review details

Configuration used: CodeRabbit UI
Review profile: ASSERTIVE

📥 Commits

Reviewing files that changed from the base of the PR and between e4750ee and 47a35b0.

📒 Files selected for processing (1)

• src/asm_files.cpp (1 hunks)

🔇 Additional comments (1)

src/asm_files.cpp (1)

248-250: 🧹 Nitpick (assertive)

Consider adding similar bounds checks in read_subprogram.

The same type of malformed relocation section could affect the read_subprogram function. Consider adding similar validation there.

[coderabbitai]

Actionable comments posted: 1

📜 Review details

Configuration used: CodeRabbit UI
Review profile: ASSERTIVE

📥 Commits

Reviewing files that changed from the base of the PR and between 47a35b0 and 33a7dcd.

📒 Files selected for processing (1)

• src/asm_files.cpp (1 hunks)

[coderabbitai]

Actionable comments posted: 1

📜 Review details

Configuration used: CodeRabbit UI
Review profile: ASSERTIVE

📥 Commits

Reviewing files that changed from the base of the PR and between 33a7dcd and b245031.

📒 Files selected for processing (1)

• src/asm_files.cpp (1 hunks)

[coveralls]

coverage: 90.125% (-0.02%) from 90.143%
when pulling 49e82a1 on dthaler:reloc-fuzz-fix
into e4750ee on vbpf:main.