Removed unnecessary lock to call acmp_process_quick in Pm::evaluate

- This was introduced in commit 119a6fc & 7d786b3 because of a potential
  issue reported in owasp-modsecurity#1573.
- The ACMP tree structure is initialized when the operator is
  initialized.
- During transaction execution the ACMP tree structure is only 'read'
  while traversing the tree (in acmp_process_quick) so this is safe for
  use in a multi-threaded environment.

Author: eduar-hte

src/operators/pm.cc

@@ -39,9 +39,6 @@ Pm::~Pm() {
 
     free(m_p);
     m_p = NULL;
-#ifdef MODSEC_MUTEX_ON_PM
-    pthread_mutex_destroy(&m_lock);
-#endif
 }
 
 
@@ -88,13 +85,7 @@ bool Pm::evaluate(Transaction *transaction, RuleWithActions *rule,
     pt.parser = m_p;
     pt.ptr = NULL;
     const char *match = NULL;
-#ifdef MODSEC_MUTEX_ON_PM
-    pthread_mutex_lock(&m_lock);
-#endif
     rc = acmp_process_quick(&pt, &match, input.c_str(), input.length());
-#ifdef MODSEC_MUTEX_ON_PM
-    pthread_mutex_unlock(&m_lock);
-#endif
 
     if (rc >= 0 && transaction) {
         std::string match_(match?match:"");
@@ -118,9 +109,6 @@ bool Pm::init(const std::string &file, std::string *error) {
     std::istringstream *iss;
     const char *err = NULL;
 
-#ifdef MODSEC_MUTEX_ON_PM
-    pthread_mutex_init(&m_lock, NULL);
-#endif
     char *content = parse_pm_content(m_param.c_str(), m_param.length(), &err);
     if (content == NULL) {
         iss = new std::istringstream(m_param);

src/operators/pm.h

@@ -52,12 +52,6 @@ class Pm : public Operator {
 
  protected:
     ACMP *m_p;
-
-#ifdef MODSEC_MUTEX_ON_PM
-
- private:
-    pthread_mutex_t m_lock;
-#endif
 };