6756528: Bytecodes::special_length_at reads past end of code buffer

Summary: Add end-of-buffer indicator for paths used by the verifier
Reviewed-by: acorn, coleenp

src/share/vm/interpreter/bytecodeStream.cpp

@@ -29,7 +29,8 @@ Bytecodes::Code RawBytecodeStream::raw_next_special(Bytecodes::Code code) {
   assert(!is_last_bytecode(), "should have been checked");
   // set next bytecode position
   address bcp = RawBytecodeStream::bcp();
-  int l = Bytecodes::raw_special_length_at(bcp);
+  address end = method()->code_base() + end_bci();
+  int l = Bytecodes::raw_special_length_at(bcp, end);
   if (l <= 0 || (_bci + l) > _end_bci) {
     code = Bytecodes::_illegal;
   } else {
@@ -39,10 +40,14 @@ Bytecodes::Code RawBytecodeStream::raw_next_special(Bytecodes::Code code) {
     _is_wide = false;
     // check for special (uncommon) cases
     if (code == Bytecodes::_wide) {
+      if (bcp + 1 >= end) {
+        code = Bytecodes::_illegal;
+      } else {
         code = (Bytecodes::Code)bcp[1];
         _is_wide = true;
       }
     }
+  }
   _code = code;
   return code;
 }

src/share/vm/interpreter/bytecodes.cpp

@@ -54,13 +54,19 @@ Bytecodes::Code Bytecodes::non_breakpoint_code_at(address bcp, methodOop method)
   return method->orig_bytecode_at(method->bci_from(bcp));
 }
 
-int Bytecodes::special_length_at(address bcp) {
+int Bytecodes::special_length_at(address bcp, address end) {
   Code code = code_at(bcp);
   switch (code) {
   case _wide:
+    if (end != NULL && bcp + 1 >= end) {
+      return -1; // don't read past end of code buffer
+    }
     return wide_length_for(cast(*(bcp + 1)));
   case _tableswitch:
     { address aligned_bcp = (address)round_to((intptr_t)bcp + 1, jintSize);
+      if (end != NULL && aligned_bcp + 3*jintSize >= end) {
+        return -1; // don't read past end of code buffer
+      }
       jlong lo = (jint)Bytes::get_Java_u4(aligned_bcp + 1*jintSize);
       jlong hi = (jint)Bytes::get_Java_u4(aligned_bcp + 2*jintSize);
       jlong len = (aligned_bcp - bcp) + (3 + hi - lo + 1)*jintSize;
@@ -73,6 +79,9 @@ int Bytecodes::special_length_at(address bcp) {
   case _fast_binaryswitch: // fall through
   case _fast_linearswitch:
     { address aligned_bcp = (address)round_to((intptr_t)bcp + 1, jintSize);
+      if (end != NULL && aligned_bcp + 2*jintSize >= end) {
+        return -1; // don't read past end of code buffer
+      }
       jlong npairs = (jint)Bytes::get_Java_u4(aligned_bcp + jintSize);
       jlong len = (aligned_bcp - bcp) + (2 + 2*npairs)*jintSize;
       // only return len if it can be represented as a positive int;
@@ -90,14 +99,17 @@ int Bytecodes::special_length_at(address bcp) {
 // verifier when reading in bytecode to verify.  Other mechanisms that
 // run at runtime (such as generateOopMaps) need to iterate over the code
 // and don't expect to see breakpoints: they want to see the instruction
-// which was replaces so that they can get the correct length and find
+// which was replaced so that they can get the correct length and find
 // the next bytecode.
-int Bytecodes::raw_special_length_at(address bcp) {
+//
+// 'end' indicates the end of the code buffer, which we should not try to read
+// past.
+int Bytecodes::raw_special_length_at(address bcp, address end) {
   Code code = code_or_bp_at(bcp);
   if (code == _breakpoint) {
     return 1;
   } else {
-    return special_length_at(bcp);
+    return special_length_at(bcp, end);
   }
 }
 

src/share/vm/interpreter/bytecodes.hpp

@@ -340,8 +340,10 @@ class Bytecodes: AllStatic {
     const char* wf = wide_format(code);
     return (wf == NULL) ? 0 : (int)strlen(wf);
   }
-  static int         special_length_at(address bcp);
-  static int         raw_special_length_at(address bcp);
+  // if 'end' is provided, it indicates the end of the code buffer which
+  // should not be read past when parsing.
+  static int         special_length_at(address bcp, address end = NULL);
+  static int         raw_special_length_at(address bcp, address end = NULL);
   static int         length_at      (address bcp)  { int l = length_for(code_at(bcp)); return l > 0 ? l : special_length_at(bcp); }
   static int         java_length_at (address bcp)  { int l = length_for(java_code_at(bcp)); return l > 0 ? l : special_length_at(bcp); }
   static bool        is_java_code   (Code code)    { return 0 <= code && code < number_of_java_codes; }