[Object/ELF] - Do not crash on invalid section index.

If object has wrong (large) string table index and
also incorrect large value for amount of sections in total,
then section index passes the check:

  if (Index >= getNumSections())
    return object_error::invalid_section_index;

But result pointer then is far after end of file data, what
result in a crash.

Differential revision: https://reviews.llvm.org/D25081

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@284369 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/Object/ELF.h b/include/llvm/Object/ELF.h
index c06fa75..31f42f5 100644 (file)
--- a/include/llvm/Object/ELF.h
+++ b/include/llvm/Object/ELF.h
@@ -399,9 +399,11 @@ ELFFile<ELFT>::getSection(uint32_t Index) const {
   if (Index >= getNumSections())
     return object_error::invalid_section_index;
 
-  return reinterpret_cast<const Elf_Shdr *>(
-      reinterpret_cast<const char *>(SectionHeaderTable) +
-      (Index * Header->e_shentsize));
+  const uint8_t *Addr = reinterpret_cast<const uint8_t *>(SectionHeaderTable) +
+                        (Index * Header->e_shentsize);
+  if (Addr >= base() + getBufSize())
+    return object_error::invalid_section_index;
+  return reinterpret_cast<const Elf_Shdr *>(Addr);
 }
 
 template <class ELFT>

diff --git a/test/Object/Inputs/invalid-section-index2.elf b/test/Object/Inputs/invalid-section-index2.elf
new file mode 100644 (file)
index 0000000..7667637
Binary files /dev/null and b/test/Object/Inputs/invalid-section-index2.elf differ

diff --git a/test/Object/invalid.test b/test/Object/invalid.test
index 9f55874..d940789 100644 (file)
--- a/test/Object/invalid.test
+++ b/test/Object/invalid.test
@@ -41,7 +41,7 @@ RUN: not llvm-readobj --dyn-symbols %p/Inputs/invalid-sh_entsize.elf 2>&1 | File
 INVALID-DYNSYM-SIZE: Invalid entity size
 
 RUN: not llvm-readobj -t %p/Inputs/invalid-section-index.elf 2>&1 | FileCheck --check-prefix=INVALID-SECTION-INDEX %s
-
+RUN: not llvm-readobj -t %p/Inputs/invalid-section-index2.elf 2>&1 | FileCheck --check-prefix=INVALID-SECTION-INDEX %s
 INVALID-SECTION-INDEX: Invalid section index
 
 RUN: not llvm-readobj -s %p/Inputs/invalid-section-size.elf 2>&1 | FileCheck --check-prefix=INVALID-SECTION-SIZE %s