[COFF] Don't reject executables with data directories pointing outside of provided data

[mstorsjo]

Summary

Before bb94611d6545c2c5271f5bb01de1aa4228a37250, we didn't check
that the sections in the COFF executable actually contained enough
raw data, when looking up what section contains tables pointed to
by the data directories.

That commit added checking, to avoid setting a pointer that points
out of bounds - by rejecting such executables.

It turns out that some binaries (e.g.g a "helper.exe" provided by
NSIS) contains a base relocation table data directory that points
into the wrong section. It points inside the virtual address space
allocated for that section, but the section contains much less raw
data, and the table points outside of the provided raw data.

No longer reject such binaries (to let tools operate on them and
inspect them), but don't set the table pointers (so that when
printing e.g. base relocations, we don't print anything).

This should fix the regression pointed out in
https://reviews.llvm.org/D126898#3565834.

[alvinhochun]

I agree with this change like I said in the linked review thread.

[mstorsjo]

@rnk - What do you think about this? See the later discussion in D126898.

The executable that triggered this was deemed to be misbuilt, but we still have the case that our tools now refuse to print/dump binaries that it tolerated before.

[rnk]

lgtm

llvm/lib/Object/COFFObjectFile.cpp

for (const SectionRef &S : sections()) {
     uint32_t SectionEnd = Section->VirtualAddress + Section->VirtualSize;
     if (SectionStart <= Addr && Addr < SectionEnd) {
       // A table/directory entry can be pointing to somewhere in a stripped
       // section, in an object that went through `objcopy --only-keep-debug`.
       // In this case we don't want to cause the parsing of the object file to
       // fail, otherwise it will be impossible to use this object as debug info
       // in LLDB. Return SectionStrippedError here so that
       // COFFObjectFile::initialize can ignore the error.
-      if (Section->SizeOfRawData == 0)
-        return make_error<SectionStrippedError>();
+      // Somewhat common binaries may have RVAs pointing outside of the
+      // provided raw data. Instead of rejecting the binaries, just
+      // treat the section as stripped for these purposes.
       if (Section->SizeOfRawData < Section->VirtualSize &&
           Addr >= SectionStart + Section->SizeOfRawData) {
-        if (ErrorContext)
-          return createStringError(object_error::parse_failed,
-                                   "RVA 0x%" PRIx32
-                                   " for %s found but data is incomplete",
-                                   Addr, ErrorContext);
-        return createStringError(
-            object_error::parse_failed,
-            "RVA 0x%" PRIx32 " found but data is incomplete", Addr);
+        return make_error<SectionStrippedError>();
       }
       uint32_t Offset = Addr - SectionStart;
       Res = reinterpret_cast<uintptr_t>(base()) + Section->PointerToRawData +
             Offset;
       return Error::success();
     }
   }
   if (ErrorContext)

llvm/test/Object/Inputs/COFF/data-dir-out-of-bounds.yaml

+--- !COFF
+OptionalHeader:  
+  AddressOfEntryPoint: 4144
+  ImageBase:       1073741824
+  SectionAlignment: 4096
+  FileAlignment:   512
+  MajorOperatingSystemVersion: 6
+  MinorOperatingSystemVersion: 0
+  MajorImageVersion: 0
+  MinorImageVersion: 0
+  MajorSubsystemVersion: 6
+  MinorSubsystemVersion: 0
+  Subsystem:       IMAGE_SUBSYSTEM_WINDOWS_CUI
+  DLLCharacteristics: [ IMAGE_DLL_CHARACTERISTICS_HIGH_ENTROPY_VA, IMAGE_DLL_CHARACTERISTICS_DYNAMIC_BASE, IMAGE_DLL_CHARACTERISTICS_NX_COMPAT, IMAGE_DLL_CHARACTERISTICS_TERMINAL_SERVER_AWARE ]
+  SizeOfStackReserve: 1048576
+  SizeOfStackCommit: 4096
+  SizeOfHeapReserve: 1048576
+  SizeOfHeapCommit: 4096
+  ExportTable:     
+    RelativeVirtualAddress: 0
+    Size:            0
+  ImportTable:     
+    RelativeVirtualAddress: 0
+    Size:            0
+  ResourceTable:   
+    RelativeVirtualAddress: 0
+    Size:            0
+  ExceptionTable:  
+    RelativeVirtualAddress: 0
+    Size:            0
+  CertificateTable: 
+    RelativeVirtualAddress: 0
+    Size:            0
+  BaseRelocationTable: 
+    RelativeVirtualAddress: 14288
+    Size:            32
+  Debug:           
+    RelativeVirtualAddress: 0
+    Size:            0
+  Architecture:    
+    RelativeVirtualAddress: 0
+    Size:            0
+  GlobalPtr:       
+    RelativeVirtualAddress: 0
+    Size:            0
+  TlsTable:        
+    RelativeVirtualAddress: 0
+    Size:            0
+  LoadConfigTable: 
+    RelativeVirtualAddress: 0
+    Size:            0
+  BoundImport:     
+    RelativeVirtualAddress: 0
+    Size:            0
+  IAT:             
+    RelativeVirtualAddress: 0
+    Size:            0
+  DelayImportDescriptor: 
+    RelativeVirtualAddress: 0
+    Size:            0
+  ClrRuntimeHeader: 
+    RelativeVirtualAddress: 0
+    Size:            0
+header:          
+  Machine:         IMAGE_FILE_MACHINE_AMD64
+  Characteristics: [ IMAGE_FILE_EXECUTABLE_IMAGE, IMAGE_FILE_LARGE_ADDRESS_AWARE ]
+sections:        
+  - Name:            .text
+    Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
+    VirtualAddress:  4096
+    VirtualSize:     87
+    SectionData:     50894C24048B0DF51F0000034C240489C859C3662E0F1F8400000000000F1F00C3662E0F1F8400000000000F1F440000554883EC30488D6C2430E8E1FFFFFFC745FC00000000B902000000E8B0FFFFFF904883C4305DC3
+  - Name:            .rdata
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ ]
+    VirtualAddress:  8192
+    VirtualSize:     20
+    SectionData:     0101010001020000010A03350A03055201500000
+  - Name:            .data
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ, IMAGE_SCN_MEM_WRITE ]
+    VirtualAddress:  12288
+    VirtualSize:     3000
+    SectionData:     '01000000'
+  - Name:            .reloc
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_DISCARDABLE, IMAGE_SCN_MEM_READ ]
+    VirtualAddress:  16384
+    VirtualSize:     32
+    SectionData:     '4DB3FFFF3090F9FF606DA6FFC69393FF'
+symbols:         []
+...

llvm/test/Object/coff-data-dir-out-of-bounds.test

+; Check an executable, where the baes relocation data directory points into
+; a section (within the range specified by VirtualSize), but outside of the
+; raw data provided in the executable. Make sure that we don't error out on
+; the executable - but we don't try to print any base relocs (as their data
+; is missing).
+
+RUN: yaml2obj %p/Inputs/COFF/data-dir-out-of-bounds.yaml | llvm-readobj --coff-basereloc - | FileCheck %s
+
+CHECK:      BaseReloc [
+CHECK-NEXT: ]