[llvm-objcopy] - Emit error and don't crash if program header reaches past end of file.

This is https://bugs.llvm.org/show_bug.cgi?id=42122.

If an object file has a size less than program header's file [offset + size]
(i.e. if we have overflow), llvm-objcopy crashes instead of reporting a
error.

The patch fixes this issue.

Differential revision: https://reviews.llvm.org/D62898

llvm-svn: 362778

test/tools/llvm-objcopy/ELF/invalid-p_filesz-p_offset.test

@@ -0,0 +1,45 @@
+## In this case, we have a program header with a file size that
+## overflows the binary size. Check llvm-objcopy doesn't crash
+## and report this error properly.
+
+# RUN: yaml2obj --docnum=1 %s -o %t1.o
+# RUN: not llvm-objcopy %t1.o 2>&1 | FileCheck %s --check-prefix=ERR1
+# ERR1: error: program header with offset 0x1b8 and file size 0x100000 goes past the end of the file
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_EXEC
+  Machine: EM_X86_64
+Sections:
+  - Name: .foo
+    Type: SHT_PROGBITS
+ProgramHeaders:
+  - Type:        PT_LOAD
+    FileSize:    0x100000
+    Sections:    
+      - Section: .foo
+
+## A similar case, but now the p_offset property of the program header is too large.
+
+# RUN: yaml2obj --docnum=2 %s -o %t2.o
+# RUN: not llvm-objcopy %t2.o 2>&1 | FileCheck %s --check-prefix=ERR2
+# ERR2: error: program header with offset 0x100000 and file size 0x1 goes past the end of the file
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_EXEC
+  Machine: EM_X86_64
+Sections:
+  - Name: .foo
+    Type: SHT_PROGBITS
+    Size: 1
+ProgramHeaders:
+  - Type:        PT_LOAD
+    Offset:      0x100000
+    FileSize:    1
+    Sections:
+      - Section: .foo

tools/llvm-objcopy/ELF/Object.cpp

@@ -1104,6 +1104,11 @@ template <class ELFT> void ELFBuilder<ELFT>::setParentSegment(Segment &Child) {
 template <class ELFT> void ELFBuilder<ELFT>::readProgramHeaders() {
   uint32_t Index = 0;
   for (const auto &Phdr : unwrapOrError(ElfFile.program_headers())) {
+    if (Phdr.p_offset + Phdr.p_filesz > ElfFile.getBufSize())
+      error("program header with offset 0x" + Twine::utohexstr(Phdr.p_offset) +
+            " and file size 0x" + Twine::utohexstr(Phdr.p_filesz) +
+            " goes past the end of the file");
+
     ArrayRef<uint8_t> Data{ElfFile.base() + Phdr.p_offset,
                            (size_t)Phdr.p_filesz};
     Segment &Seg = Obj.addSegment(Data);