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Harden dumpDebugLoc against malformed .debug_loc sections

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  • Algo errado?
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Avaliação

Dificuldade
3/5
Tempo estimado
1-2 dias
Facilidade para iniciantes
45/100
Tipo de issue
Bug
Clareza
Razoavelmente clara
Status de atividade
Ativa
Stack de tecnologia
cpp, wasm
Domínio
compilers

Direção de pesquisa

Start in dumpDebugLoc in third_party/llvm-project/dwarf2yaml.cpp, where the exit(1) on a null list sits, and read parseOneLocationList to see how entry.Loc is sized before the copy. Check how the address size is taken from the first CU. Done means a malformed list prints a warning and skips the rest of the section instead of exiting, the entry.Loc length is bounded, and a debug-build assert covers the shared address size. The issue does not give the length limit, so that needs a maintainer decision.

Escrita pelo modelo de indexação a partir do texto da issue.

Descrição

Background:

#6879 was a SIGSEGV in dumpDebugLoc for modules with empty .debug_loc
sections. Fixed by #7910 with a null-CU guard. While reviewing that fix,
three defensive improvements to the same function became apparent. None
is a regression, but each turns a malformed-input case into a hard
failure when it could fail gracefully.

Location: third_party/llvm-project/dwarf2yaml.cpp, dumpDebugLoc.

  1. exit(1) on parse failure.

    if (!list) {
  errs() << "debug_loc error\n";
  exit(1);
}

    A single malformed location list aborts the entire wasm-opt run. A
    warning plus break (skip the rest of the section) would let the tool
    finish processing the module with incomplete debug info, which is
    the behavior for every other diagnostic in wasm-opt.

  2. Unbounded copy of location expression bytes.

    entry.Loc is read from the section by parseOneLocationList. There is
    no upper bound on its length before the copy into loc.Location. A
    malformed length field causes unbounded allocation.

  3. Address-size heuristic.

    The comment "should be ok since they all have the same address size?"
    is a heuristic. All CUs in well-formed modules share the same
    AddrSize, so reading it from the first CU is safe in practice, but
    the assumption is not enforced.

Proposed changes:

  • Replace exit(1) with a warning and break.
  • Add a length sanity check before copying entry.Loc.
  • Promote the address-size comment from a question to an explicit
    assumption with a debug-build assert.

Refs #6879, #7910.

Linguagem predominante
WebAssembly
Estrelas
8.7k
Forks
895
Merge médio
1d 22h
PRs com merge (30d)
97

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