[Object/ELF] - Fixed behavior when SectionHeaderTable->sh_size is too large.

[grimar]

Summary

Elf.h already has code checking that section table does not go past end of file.
Problem is that this check may not work on values greater than UINT64_MAX / Header->e_shentsize
because of calculation overflow.

Parch fixes the issue.

[• rafael]

LGTM

llvm/trunk/include/llvm/Object/ELF.h

if (SectionTableOffset & (alignof(Elf_Shdr) - 1)) {
     // Invalid address alignment of section headers
     EC = object_error::parse_failed;
     return;
   }
 
   // The getNumSections() call below depends on SectionHeaderTable being set.
   SectionHeaderTable =
     reinterpret_cast<const Elf_Shdr *>(base() + SectionTableOffset);
+  if (getNumSections() > UINT64_MAX / Header->e_shentsize) {
+    // Section table goes past end of file!
+    EC = object_error::parse_failed;
+    return;
+  }
+
   const uint64_t SectionTableSize = getNumSections() * Header->e_shentsize;
 
   if (SectionTableOffset + SectionTableSize > FileSize) {
     // Section table goes past end of file!
     EC = object_error::parse_failed;
     return;
   }
 

llvm/trunk/test/Object/invalid.test

 
 RUN: not llvm-readobj -t %p/Inputs/invalid-sections-address-alignment.x86-64 2>&1 | \
 RUN:   FileCheck --check-prefix=INVALID-SEC-ADDRESS-ALIGNMENT %s
 INVALID-SEC-ADDRESS-ALIGNMENT: Invalid data was encountered while parsing the file
 
 RUN: not llvm-readobj -t %p/Inputs/invalid-section-size2.elf 2>&1 | \
 RUN:   FileCheck --check-prefix=INVALID-SECTION-SIZE2 %s
 INVALID-SECTION-SIZE2: Invalid data was encountered while parsing the file.
+
+RUN: not llvm-readobj -t %p/Inputs/invalid-sections-num.elf 2>&1 | FileCheck --check-prefix=INVALID-SECTION-NUM %s
+INVALID-SECTION-NUM: Invalid data was encountered while parsing the file.