fix #14352: fuzzing crash (null-pointer-use) in Preprocessor::simplifyPragmaAsmPrivate() (danmar#8075)

Author: ludviggunne

lib/preprocessor.cpp

@@ -1070,6 +1070,7 @@ void Preprocessor::simplifyPragmaAsmPrivate(simplecpp::TokenList &tokenList)
             continue;
 
         const simplecpp::Token *endasm = tok3;
+        bool foundEndasm = false;
         while ((endasm = endasm->next) != nullptr) {
             if (endasm->op != '#' || sameline(endasm,endasm->previousSkipComments()))
                 continue;
@@ -1081,9 +1082,13 @@ void Preprocessor::simplifyPragmaAsmPrivate(simplecpp::TokenList &tokenList)
                 continue;
             while (sameline(endasm,endasm3))
                 endasm = endasm->next;
+            foundEndasm = true;
             break;
         }
 
+        if (!foundEndasm)
+            throw InternalError(nullptr, "syntax error: missing #pragma endasm", InternalError::SYNTAX);
+
         const simplecpp::Token * const tok4 = tok3->next;
         tok->setstr("asm");
         const_cast<simplecpp::Token *>(tok2)->setstr("(");

test/cli/fuzz-crash/crash-ef635709a2489083534cd422e6a089daab23ec64

@@ -0,0 +1 @@
+#pragma asm

test/testpreprocessor.cpp

@@ -365,6 +365,8 @@ class TestPreprocessor : public TestFixture {
         TEST_CASE(standard);
 
         TEST_CASE(writeLocations);
+
+        TEST_CASE(pragmaAsm);
     }
 
     template<size_t size>
@@ -2804,6 +2806,12 @@ class TestPreprocessor : public TestFixture {
             "} ;",
             processed);
     }
+
+    void pragmaAsm()
+    {
+        const char code[] = "#pragma asm";
+        ASSERT_THROW_INTERNAL(getcodeforcfg(settingsDefault, *this, code, "", "test.cpp"), InternalError::SYNTAX);
+    }
 };
 
 REGISTER_TEST(TestPreprocessor)