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Object: avoid undefined behavior when bounds-checking

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Don't form an out of bounds pointer just to test if it
would be out of bounds.

Also perform the same bounds checking for all the previous
mapped structures.

llvm-svn: 149750
This commit is contained in:
Dylan Noblesmith 2012-02-04 02:41:39 +00:00
parent 734d2c47b0
commit 2692a852bb
1 changed files with 23 additions and 9 deletions
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32
lib/Object/ELFObjectFile.cpp
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@ -1173,25 +1173,36 @@ ELFObjectFile<target_endianness, is64Bits>::ELFObjectFile(MemoryBuffer *Object
, SectionHeaderTable(0)
, dot_shstrtab_sec(0)
, dot_strtab_sec(0) {
const uint64_t FileSize = Data->getBufferSize();
if (sizeof(Elf_Ehdr) > FileSize)
// FIXME: Proper error handling.
report_fatal_error("File too short!");
Header = reinterpret_cast<const Elf_Ehdr *>(base());
if (Header->e_shoff == 0)
return;
SectionHeaderTable =
reinterpret_cast<const Elf_Shdr *>(base() + Header->e_shoff);
uint64_t SectionTableSize = getNumSections() * Header->e_shentsize;
const uint64_t SectionTableOffset = Header->e_shoff;
if ((const uint8_t *)SectionHeaderTable + SectionTableSize
> base() + Data->getBufferSize()) {
if (SectionTableOffset + sizeof(Elf_Shdr) > FileSize)
// FIXME: Proper error handling.
report_fatal_error("Section header table goes past end of file!");
// The getNumSections() call below depends on SectionHeaderTable being set.
SectionHeaderTable =
reinterpret_cast<const Elf_Shdr *>(base() + SectionTableOffset);
const uint64_t SectionTableSize = getNumSections() * Header->e_shentsize;
if (SectionTableOffset + SectionTableSize > FileSize)
// FIXME: Proper error handling.
report_fatal_error("Section table goes past end of file!");
}
// To find the symbol tables we walk the section table to find SHT_SYMTAB.
const Elf_Shdr* SymbolTableSectionHeaderIndex = 0;
const Elf_Shdr* sh = reinterpret_cast<const Elf_Shdr*>(SectionHeaderTable);
const Elf_Shdr* sh = SectionHeaderTable;
for (uint64_t i = 0, e = getNumSections(); i != e; ++i) {
if (sh->sh_type == ELF::SHT_SYMTAB_SHNDX) {
if (SymbolTableSectionHeaderIndex)
@ -1357,8 +1368,11 @@ unsigned ELFObjectFile<target_endianness, is64Bits>::getArch() const {
template<support::endianness target_endianness, bool is64Bits>
uint64_t ELFObjectFile<target_endianness, is64Bits>::getNumSections() const {
if (Header->e_shnum == ELF::SHN_UNDEF)
assert(Header && "Header not initialized!");
if (Header->e_shnum == ELF::SHN_UNDEF) {
assert(SectionHeaderTable && "SectionHeaderTable not initialized!");
return SectionHeaderTable->sh_size;
}
return Header->e_shnum;
}