Recommit rr366796 "[Object/ELF.h] - Improve testing of the fields in ELFFile<ELFT>::sections()."

With a fix of the issue found by UBSan.

Original commit message:

This eliminates a one error untested and
also introduces a error for one more possible case
which lead to crash previously.

Differential revision: https://reviews.llvm.org/D64987

llvm-svn: 366886

llvm/include/llvm/Object/ELF.h

@@ -495,7 +495,8 @@ Expected<typename ELFT::ShdrRange> ELFFile<ELFT>::sections() const {
                        Twine(getHeader()->e_shentsize));
 
   const uint64_t FileSize = Buf.size();
-  if (SectionTableOffset + sizeof(Elf_Shdr) > FileSize)
+  if (SectionTableOffset + sizeof(Elf_Shdr) > FileSize ||
+      SectionTableOffset + (uintX_t)sizeof(Elf_Shdr) < SectionTableOffset)
     return createError(
         "section header table goes past the end of the file: e_shoff = 0x" +
         Twine::utohexstr(SectionTableOffset));
@@ -513,15 +514,22 @@ Expected<typename ELFT::ShdrRange> ELFFile<ELFT>::sections() const {
     NumSections = First->sh_size;
 
   if (NumSections > UINT64_MAX / sizeof(Elf_Shdr))
-    // TODO: this error is untested.
+    return createError("invalid number of sections specified in the NULL "
-    return createError("section table goes past the end of file");
+                       "section's sh_size field (" +
+                       Twine(NumSections) + ")");
 
   const uint64_t SectionTableSize = NumSections * sizeof(Elf_Shdr);
+  if (SectionTableOffset + SectionTableSize < SectionTableOffset)
+    return createError(
+        "invalid section header table offset (e_shoff = 0x" +
+        Twine::utohexstr(SectionTableOffset) +
+        ") or invalid number of sections specified in the first section "
+        "header's sh_size field (0x" +
+        Twine::utohexstr(NumSections) + ")");
 
   // Section table goes past end of file!
   if (SectionTableOffset + SectionTableSize > FileSize)
     return createError("section table goes past the end of file");
-
   return makeArrayRef(First, NumSections);
 }
 

llvm/include/llvm/ObjectYAML/ELFYAML.h

@@ -77,7 +77,7 @@ struct FileHeader {
   llvm::yaml::Hex64 Entry;
 
   Optional<llvm::yaml::Hex16> SHEntSize;
-  Optional<llvm::yaml::Hex16> SHOffset;
+  Optional<llvm::yaml::Hex64> SHOffset;
   Optional<llvm::yaml::Hex16> SHNum;
   Optional<llvm::yaml::Hex16> SHStrNdx;
 };

llvm/test/Object/invalid.test

@@ -552,3 +552,57 @@ FileHeader:
 Sections:
   - Name: .foo
     Type: SHT_PROGBITS
+
+## We report an error if the number of sections stored in sh_size
+## is greater than UINT64_MAX / sizeof(Elf_Shdr) == 288230376151711743.
+## Here we check that do not crash on a border value.
+
+# RUN: yaml2obj --docnum=26 %s -o %t26
+# RUN: not llvm-readobj -h %t26 2>&1 | FileCheck -DFILE=%t26 --check-prefix=INVALID-SEC-NUM1 %s
+
+# INVALID-SEC-NUM1: error: '[[FILE]]': invalid section header table offset (e_shoff = 0x40) or invalid number of sections specified in the first section header's sh_size field (0x3ffffffffffffff)
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_REL
+  Machine: EM_X86_64
+  SHNum:   0x0
+Sections:
+  - Type: SHT_NULL
+    Size: 288230376151711743
+
+## See above, but now we test the UINT64_MAX / sizeof(Elf_Shdr) value.
+## The error is slightly different in this case.
+
+# RUN: yaml2obj --docnum=27 %s -o %t27
+# RUN: not llvm-readobj -h %t27 2>&1 | FileCheck -DFILE=%t27 --check-prefix=INVALID-SEC-NUM2 %s
+
+# INVALID-SEC-NUM2: error: '[[FILE]]': invalid number of sections specified in the NULL section's sh_size field (288230376151711744)
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_REL
+  Machine: EM_X86_64
+  SHNum:   0x0
+Sections:
+  - Type: SHT_NULL
+    Size: 288230376151711744
+
+## Check the case when SHOffset is too large. SHOffset + sizeof(Elf_Shdr) overflows the uint64 type.
+
+# RUN: yaml2obj --docnum=28 %s -o %t28
+# RUN: not llvm-readobj -h %t28 2>&1 | FileCheck -DFILE=%t28 --check-prefix=INVALID-SEC-NUM3 %s
+
+# INVALID-SEC-NUM3: error: '[[FILE]]': section header table goes past the end of the file: e_shoff = 0xffffffffffffffff
+ 
+--- !ELF
+FileHeader:
+  Class:    ELFCLASS64
+  Data:     ELFDATA2LSB
+  Type:     ET_REL
+  Machine:  EM_X86_64
+  SHOffset: 0xffffffffffffffff

llvm/tools/yaml2obj/yaml2elf.cpp

@@ -244,7 +244,7 @@ void ELFState<ELFT>::initELFHeader(Elf_Ehdr &Header) {
   // Immediately following the ELF header and program headers.
   Header.e_shoff =
       Doc.Header.SHOffset
-          ? (uint16_t)*Doc.Header.SHOffset
+          ? (typename ELFT::uint)(*Doc.Header.SHOffset)
           : sizeof(Header) + sizeof(Elf_Phdr) * Doc.ProgramHeaders.size();
   Header.e_shnum =
       Doc.Header.SHNum ? (uint16_t)*Doc.Header.SHNum : SN2I.size() + 1;