[ELF2] - fixed infinite includes depth (in linkerscript)

[grimar]

Summary

Infinite including leads to out of memory after hard freeze because of infinite loop. According to specs INCLUDE should be limited to 10 levels depth.

[ruiu]

Adding a marker string to the vector which otherwise contain only real tokens is too hacky. The linker script handler is intentionally dumb and simple. Please leave it alone now.

[grimar]

In D13872#270287, @ruiu wrote:

Adding a marker string to the vector which otherwise contain only real tokens is too hacky. The linker script handler is intentionally dumb and simple. Please leave it alone now.

But I compare address of first element, not the token values:

if (Tok.begin() == EndInclude.begin())

That should not affect the real tokens..

[ruiu]

Yes I know. This change itself is correct. It's that I don't want to add more safeguard code here as all code in this file will soon be rewritten when we start working on real implementation.

[grimar]

Ok then..

ELF/LinkerScript.cpp

private:
   void readOutput();
   void readOutputArch();
   void readOutputFormat();
   void readSearchDir();
 
   StringSaver Saver;
   std::vector<StringRef> Tokens;
   size_t Pos = 0;
+  size_t IncludeLevel = 0;
 };
+
+StringRef EndInclude = "_end_include";
 }
 
 void LinkerScript::run() {
   while (!atEOF()) {
     StringRef Tok = next();
     if (Tok == ";")
       continue;
+    if (Tok.begin() == EndInclude.begin()) {
+      --IncludeLevel;
+      continue;
+    }
     if (Tok == "ENTRY") {
       readEntry();
     } else if (Tok == "GROUP" || Tok == "INPUT") {
       readGroup();
     } else if (Tok == "INCLUDE") {
       readInclude();
     } else if (Tok == "OUTPUT") {
       readOutput();
if (Tok == "AS_NEEDED") {
       readAsNeeded();
       continue;
     }
     addFile(Tok);
   }
 }
 
 void LinkerScript::readInclude() {
+  ++IncludeLevel;
+  if (IncludeLevel > 10) {
+    error("includes nested too deeply");
+  }
   StringRef Tok = next();
   auto MBOrErr = MemoryBuffer::getFile(Tok);
   error(MBOrErr, "cannot open " + Tok);
   std::unique_ptr<MemoryBuffer> &MB = *MBOrErr;
   StringRef S = Saver.save(MB->getMemBufferRef().getBuffer());
   std::vector<StringRef> V = tokenize(S);
+  V.push_back(EndInclude);
   Tokens.insert(Tokens.begin() + Pos, V.begin(), V.end());
 }
 
 void LinkerScript::readOutput() {
   // -o <file> takes predecence over OUTPUT(<file>).
   expect("(");
   StringRef Tok = next();
   if (Config->OutputFile.empty())

test/elf2/linkerscript.s

 # RUN: echo "INCLUDE " %t.script2 "OUTPUT(" %t.out ")" > %t.script1
 # RUN: echo "GROUP(" %t ")" > %t.script2
 # RUN: ld.lld2 %t.script1
 # RUN: llvm-readobj %t2 > /dev/null
 
 # RUN: echo "FOO(BAR)" > %t.script
 # RUN: not ld.lld2 -o foo %t.script > %t.log 2>&1
 # RUN: FileCheck -check-prefix=ERR1 %s < %t.log
-
 # ERR1: unknown directive: FOO
 
+# RUN: echo "INCLUDE " %t.script > %t.script
+# RUN: not ld.lld2 -o %t2 %t.script > %t.log 2>&1
+# RUN: FileCheck -check-prefix=ERR2 %s < %t.log
+# ERR2: includes nested too deeply
+
 .globl _start, _label;
 _start:
   mov $60, %rax
   mov $42, %rdi
 _label:
   syscall