[PATCH] D25462: [Object/ELF] - Check Header->e_shoff value earlier and do not crash.

[George Rimar via llvm-commits]

grimar created this revision.
grimar added reviewers: rafael, davide.
grimar added subscribers: llvm-commits, grimar, evgeny777.

I had to revert https://reviews.llvm.org/D25368 (r283858, r283740) because it was the reason of UBSan failture:
(http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-fast/builds/17075)

-

Exit Code: 1

Command Output (stderr):
------------------------

/mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm/test/Object/invalid.test:70:32: error: expected string not found in input
INVALID-SEC-ADDRESS-ALIGNMENT: Invalid address alignment of section headers

  ^

<stdin>:1:1: note: scanning from here
/mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm/include/llvm/Object/ELF.h:412:7: runtime error: upcast of misaligned address 0x000002d8b899 for type 'llvm::object::Elf_Shdr_Impl<llvm::object::ELFType<llvm::support::endianness::little, true> >', which requires 2 byte alignment
^
<stdin>:1:125: note: possible intended match here
/mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm/include/llvm/Object/ELF.h:412:7: runtime error: upcast of misaligned address 0x000002d8b899 for type 'llvm::object::Elf_Shdr_Impl<llvm::object::ELFType<llvm::support::endianness::little, true> >', which requires 2 byte alignment

            

Problem is seems to be that on the moment of following call, Section pointer is unaligned:

  ELFFile<ELFT>::getStringTable(const Elf_Shdr *Section) const

Patch moves the alignment check before such call to fix the issue.


https://reviews.llvm.org/D25462

Files:
  include/llvm/Object/ELF.h
  test/Object/Inputs/invalid-sections-address-alignment.x86-64
  test/Object/invalid.test


Index: test/Object/invalid.test
===================================================================
--- test/Object/invalid.test
+++ test/Object/invalid.test
@@ -64,3 +64,7 @@
 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 data was encountered while parsing the file
+
+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
Index: include/llvm/Object/ELF.h
===================================================================
--- include/llvm/Object/ELF.h
+++ include/llvm/Object/ELF.h
@@ -330,6 +330,12 @@
     return;
   }
 
+  if (SectionTableOffset & (AlignOf<Elf_Shdr>::Alignment - 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);


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