Merge pull request #859 from pi-hole/fix/domainstring_validity

Create and use a temporary copy of the domain string during the analysis

src/dnsmasq_interface.c

@@ -142,7 +142,7 @@ static bool _FTL_check_blocking(int queryID, int domainID, int clientID, const c
  // Skip the entire chain of tests if we already know the answer for this
  // particular client
  unsigned char blockingStatus = dns_cache->blocking_status;
- const char* domainstr = getstr(domain->domainpos);
+ char *domainstr = (char*)getstr(domain->domainpos);
  switch(blockingStatus)
  {
  case UNKNOWN_BLOCKED:
@@ -252,8 +252,13 @@ static bool _FTL_check_blocking(int queryID, int domainID, int clientID, const c
  return false;
  }
 
- // Check whitelist (exact + regex) for match
+ // Make a local copy of the domain string. The string memory may get
+ // reorganized in the following. We cannot expect domainstr to remain
+ // valid for all time.
+ domainstr = strdup(domainstr);
  const char *blockedDomain = domainstr;
+
+ // Check whitelist (exact + regex) for match
  query->whitelisted = in_whitelist(domainstr, clientID, client);
 
  bool blockDomain = false;
@@ -299,6 +304,7 @@ static bool _FTL_check_blocking(int queryID, int domainID, int clientID, const c
  dns_cache->blocking_status = query->whitelisted ? WHITELISTED : NOT_BLOCKED;
  }
 
+ free(domainstr);
  return blockDomain;
 }