[ELF] - Do not crash on invalid symbol index.

[grimar]

Summary

Relative to PR30540.

If .symtab has invalid type in elf, no bodies are created and any relocation
that tries to access them will fail.
The same can happen if symbol index is just incorrect.

This was revealed by "id_000005,sig_11,src_000000,op_flip2,pos_420"

[grimar]

• Rebased.
• Run afl-min on testcases (had no any changes in size).

[ruiu]

ELF/InputFiles.h

154–155

In the previous patch, you checked a value in a constructor of a symbol class. Here, you are checking it in InputFile. That seems inconsistent. Probably we should do all error checking in InputFile.cpp?

[grimar]

ELF/InputFiles.h

154–155

In a construnctor of DefinedCommon, right. Because st_value contains alignment if symbol is SHT_COMMON and I tried to isolate check.

We know that symbol is common somewhere in ObjectFile<ELFT>::createSymbolBody() first time I think. Do you think it is better to have check there:

case SHN_COMMON:
  // Here ?
  return elf::Symtab<ELFT>::X
      ->addCommon(Name, Sym->st_size, Sym->st_value, Binding, Sym->st_other,
                  Sym->getType(), this)
      ->body();

I think constructor or SymbolTable::addCommon are more isolated and convenient places for checks.
Do you think we should change D25085 ?

[grimar]

• Removed excessive test.

[• rafael]

LGTM

[ruiu]

LGTM

ELF/InputFiles.h

155

Please include the filename.

ELF/InputFiles.h

public:
 
   explicit ObjectFile(MemoryBufferRef M);
   void parse(llvm::DenseSet<StringRef> &ComdatGroups);
 
   ArrayRef<InputSectionBase<ELFT> *> getSections() const { return Sections; }
   InputSectionBase<ELFT> *getSection(const Elf_Sym &Sym) const;
 
   SymbolBody &getSymbolBody(uint32_t SymbolIndex) const {
+    if (SymbolIndex >= SymbolBodies.size())
+      fatal("invalid symbol index");
     return *SymbolBodies[SymbolIndex];
   }
 
   template <typename RelT> SymbolBody &getRelocTargetSym(const RelT &Rel) const {
     uint32_t SymIndex = Rel.getSymbol(Config->Mips64EL);
     return getSymbolBody(SymIndex);
   }
 

test/ELF/invalid/invalid-symbol-index.s

+## invalid-symbol-index.elf has incorrect type of .symtab section:
+## Section Headers:
+##   [Nr] Name              Type            Address          Off    Size   ES Flg Lk Inf Al
+##   [ 0]                   NULL            0000000000000000 000000 000000 00      0   0  0
+## ...
+##   [ 4] .symtab           RELA            0000000000000000 000048 000030 18      1   2  8
+## There is no symbol bodies because of that but relocations resolution tries to access them.
+# RUN: not ld.lld %p/Inputs/invalid-symbol-index.elf -o %t2 2>&1 | \
+# RUN:   FileCheck --check-prefix=INVALID-SYMBOL-INDEX %s
+# INVALID-SYMBOL-INDEX: invalid symbol index
+
+## invalid-symbol-index2.elf just contains wrong symbol index in relocation:
+## Relocation section '.rela.text' at offset 0x1c0 contains 1 entries:
+##     Offset             Info             Type               Symbol's Value  Symbol's Name + Addend
+## 0000000000000123  000000ff00000002 R_X86_64_PC32          bad symbol index: 000000ff
+## 
+## Symbol table '.symtab' contains 1 entries:
+##    Num:    Value          Size Type    Bind   Vis      Ndx Name
+##      0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND 
+# RUN: not ld.lld %p/Inputs/invalid-symbol-index2.elf -o %t2 2>&1 | \
+# RUN:   FileCheck --check-prefix=INVALID-SYMBOL-INDEX %s