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Harden dumpDebugLoc against malformed .debug_loc sections

Aperta
  • Qualcosa non va?
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Valutazione

Difficoltà
3/5
Tempo stimato
1-2 giorni
Idoneità per principianti
45/100
Tipo di issue
Bug
Chiarezza
Abbastanza chiara
Stato di attività
Attiva
Stack tecnologico
cpp, wasm
Ambito
compilers

Direzione di ricerca

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.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Descrizione

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.

Lingua principale
WebAssembly
Stelle
8.7k
Fork
895
Merge medio
1g 22h
PR unite (30g)
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