[Object/ELF] - Do not crash on invalid sh_size value of REL[A] section.

[grimar]

Summary

Previously code would access invalid memory and may crash,
patch fixes the issue.
Was noticed by Rafael Ávila de Espíndola in comments for D25187.

[grimar]

• Fixed bug.

[grimar]

I suggest different solution: D25315

[grimar]

Since generic approach from D25315 was rejected, reclaiming this one.

[• rafael]

I think r283454 fixed this, no?

[grimar]

r283454 fixes that.

include/llvm/Object/ELF.h

if (sec->sh_offset >= Buf.size())
       report_fatal_error("Invalid relocation entry offset");
     return reinterpret_cast<const Elf_Rela *>(base() + sec->sh_offset);
   }
 
   const Elf_Rela *rela_end(const Elf_Shdr *sec) const {
     uint64_t Size = sec->sh_size;
     if (Size % sizeof(Elf_Rela))
       report_fatal_error("Invalid relocation table size");
-    return rela_begin(sec) + Size / sizeof(Elf_Rela);
+    const Elf_Rela *Begin = rela_begin(sec);
+    if (reinterpret_cast<const uint8_t *>(Begin + Size) >= base() + Buf.size())
+      report_fatal_error("Invalid relocation entry size");
+    return Begin + Size / sizeof(Elf_Rela);
   }
 
   Elf_Rela_Range relas(const Elf_Shdr *Sec) const {
     return makeArrayRef(rela_begin(Sec), rela_end(Sec));
   }
 
   const Elf_Rel *rel_begin(const Elf_Shdr *sec) const {
     if (sec->sh_entsize != sizeof(Elf_Rel))
       report_fatal_error("Invalid relocation entry size");
     if (sec->sh_offset >= Buf.size())
       report_fatal_error("Invalid relocation entry offset");
     return reinterpret_cast<const Elf_Rel *>(base() + sec->sh_offset);
   }
 
   const Elf_Rel *rel_end(const Elf_Shdr *sec) const {
     uint64_t Size = sec->sh_size;
     if (Size % sizeof(Elf_Rel))
       report_fatal_error("Invalid relocation table size");
-    return rel_begin(sec) + Size / sizeof(Elf_Rel);
+    const Elf_Rel *Begin = rel_begin(sec);
+    if (reinterpret_cast<const uint8_t *>(Begin + Size) >= base() + Buf.size())
+      report_fatal_error("Invalid relocation entry size");
+    return Begin + Size / sizeof(Elf_Rel);
   }
 
   Elf_Rel_Range rels(const Elf_Shdr *Sec) const {
     return makeArrayRef(rel_begin(Sec), rel_end(Sec));
   }
 
   /// \brief Iterate over program header table.
   const Elf_Phdr *program_header_begin() const {

test/Object/invalid.test

 RUN:   FileCheck --check-prefix=INVALID-EXT-SYMTAB-INDEX %s
 INVALID-EXT-SYMTAB-INDEX: Invalid symbol table index
 
 RUN: not llvm-readobj -r %p/Inputs/invalid-relocation-sec-sh_offset.elf-i386 2>&1 | \
 RUN:   FileCheck --check-prefix=INVALID-RELOC-SH-OFFSET %s
 RUN: not llvm-readobj -r %p/Inputs/invalid-relocation-sec-sh_offset.elf-x86-64 2>&1 | \
 RUN:   FileCheck --check-prefix=INVALID-RELOC-SH-OFFSET %s
 INVALID-RELOC-SH-OFFSET: Invalid relocation entry offset
+
+RUN: not llvm-readobj -r %p/Inputs/invalid-relocation-sec-sh_size.elf-i386 2>&1 | \
+RUN:   FileCheck --check-prefix=INVALID-RELOC-SH-SIZE %s
+RUN: not llvm-readobj -r %p/Inputs/invalid-relocation-sec-sh_size.elf-x86-64 2>&1 | \
+RUN:   FileCheck --check-prefix=INVALID-RELOC-SH-SIZE %s
+INVALID-RELOC-SH-SIZE: Invalid relocation entry size