Commit 327c4450 authored by Georgii Rymar's avatar Georgii Rymar
Browse files

[llvm-readobj] - Verify the location of program headers better. 

This improves condition in the ELFFile::program_headers().
Previously if was possible to read the headers from the wrong place when
the value of e_phoff was so large that computation overflowed.

Differential revision: https://reviews.llvm.org/D83774
parent f6eb5daa

llvm/include/llvm/Object/ELF.h

+7 −5
Original line number Diff line number Diff line
@@ -205,16 +205,18 @@ public: 
    if (getHeader()->e_phnum && getHeader()->e_phentsize != sizeof(Elf_Phdr))

      return createError("invalid e_phentsize: " +

                         Twine(getHeader()->e_phentsize));

    if (getHeader()->e_phoff +

            (getHeader()->e_phnum * getHeader()->e_phentsize) >

        getBufSize())



    uint64_t HeadersSize =

        (uint64_t)getHeader()->e_phnum * getHeader()->e_phentsize;

    uint64_t PhOff = getHeader()->e_phoff;

    if (PhOff + HeadersSize < PhOff || PhOff + HeadersSize > getBufSize())

      return createError("program headers are longer than binary of size " +

                         Twine(getBufSize()) + ": e_phoff = 0x" +

                         Twine::utohexstr(getHeader()->e_phoff) +

                         ", e_phnum = " + Twine(getHeader()->e_phnum) +

                         ", e_phentsize = " + Twine(getHeader()->e_phentsize));

    auto *Begin =

        reinterpret_cast<const Elf_Phdr *>(base() + getHeader()->e_phoff);



    auto *Begin = reinterpret_cast<const Elf_Phdr *>(base() + PhOff);

    return makeArrayRef(Begin, Begin + getHeader()->e_phnum);

  }

llvm/test/tools/llvm-readobj/ELF/gnu-phdrs.test

+29 −2
Original line number Diff line number Diff line
@@ -356,7 +356,8 @@ ProgramHeaders: 
    Offset: 0xAABBCCDDEEFF1122



## Check we report a warning when we are unable to read program headers.

# RUN: yaml2obj --docnum=3 %s -o %t.phdr.err

## Case A: the e_phentsize field is invalid.

# RUN: yaml2obj --docnum=3 -DPHENTSIZE=1 %s -o %t.phdr.err

# RUN: llvm-readelf --program-headers %t.phdr.err 2>&1 | \

# RUN:   FileCheck %s -DFILE=%t.phdr.err --check-prefix=WARN-PHENTSIZE
@@ -373,7 +374,8 @@ FileHeader: 
  Data:       ELFDATA2LSB

  Type:       ET_EXEC

  Machine:    EM_X86_64

  EPhEntSize: 1

  EPhEntSize: [[PHENTSIZE=56]]

  EPhOff:     [[PHOFF=64]]

Sections:

  - Name: .foo

    Type: SHT_PROGBITS
@@ -381,3 +383,28 @@ ProgramHeaders: 
  - Type: PT_PHDR

    Sections:

      - Section: .foo



## Case B: the value of the e_phoff field is invalid.



## Check that we do not report a warning when the program header table ends right before the end of the file.

## 0x160 + size of headers (56) == file size.

# RUN: yaml2obj --docnum=3 -DPHOFF=0x160 %s -o %t.phdr.no.err2

# RUN: llvm-readelf %t.phdr.no.err2 --program-headers 2>&1 | FileCheck %s --implicit-check-not=warning:



## Check we report a warning when e_phoff goes 1 byte past the end of the file.

# RUN: yaml2obj --docnum=3 -DPHOFF=0x161 %s -o %t.phdr.err2

# RUN: llvm-readelf --program-headers %t.phdr.err2 2>&1 | \

# RUN:   FileCheck %s -DFILE=%t.phdr.err2 --check-prefix=WARN-PHOFF -DOFF=0x161



# WARN-PHOFF:      Program Headers:

# WARN-PHOFF-NEXT:   Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align

# WARN-PHOFF-NEXT: warning: '[[FILE]]': unable to dump program headers: program headers are longer than binary of size 408: e_phoff = [[OFF]], e_phnum = 1, e_phentsize = 56

# WARN-PHOFF:      Section to Segment mapping:

# WARN-PHOFF-NEXT:   Segment Sections...

# WARN-PHOFF-NEXT: warning: '[[FILE]]': can't read program headers to build section to segment mapping: program headers are longer than binary of size 408: e_phoff = [[OFF]], e_phnum = 1, e_phentsize = 56



## Check we report a warning when the value of e_phoff is so large that

## e_phoff + e_phnum * e_phentsize > UINT64_MAX.

# RUN: yaml2obj --docnum=3 -DPHOFF=0xffffffffffffffff %s -o %t.phdr.err3

# RUN: llvm-readelf --program-headers %t.phdr.err3 2>&1 | \

# RUN:   FileCheck %s -DFILE=%t.phdr.err3 --check-prefix=WARN-PHOFF -DOFF=0xffffffffffffffff