Re-aquire client and upstream pointers after a name resolution. As we…

…'re leaving the locked area for the resolve, we cannot control if the shared memory object changed meanwhile. If it did, then the pointers will point into nowhere, leading to a SEGV_MAPERR.

Signed-off-by: DL6ER <dl6er@dl6er.de>

src/resolve.c

@@ -302,17 +302,17 @@ void resolveClients(const bool onlynew)
  int skipped = 0;
  for(int clientID = 0; clientID < clientscount; clientID++)
  {
- // Get client pointer
+ // Memory access needs to get locked
+ lock_shm();
+ // Get client pointer for the first time (reading data)
  clientsData* client = getClient(clientID, true);
  if(client == NULL)
  {
- logg("ERROR: Unable to get client pointer with ID %i, skipping...", clientID);
+ logg("ERROR: Unable to get client pointer (1) with ID %i, skipping...", clientID);
  skipped++;
  continue;
  }
 
- // Memory access needs to get locked
- lock_shm();
  bool newflag = client->new;
  size_t ippos = client->ippos;
  size_t oldnamepos = client->namepos;
@@ -330,6 +330,18 @@ void resolveClients(const bool onlynew)
  size_t newnamepos = resolveAndAddHostname(ippos, oldnamepos);
 
  lock_shm();
+ // Get client pointer for the second time (writing data)
+ // We cannot use the same pointer again as we released
+ // the lock in between so we cannot know if something
+ // happened to the shared memory object (resize event)
+ client = getClient(clientID, true);
+ if(client == NULL)
+ {
+ logg("ERROR: Unable to get client pointer (2) with ID %i, skipping...", clientID);
+ skipped++;
+ continue;
+ }
+
  // Store obtained host name (may be unchanged)
  client->namepos = newnamepos;
  // Mark entry as not new
@@ -355,7 +367,9 @@ void resolveForwardDestinations(const bool onlynew)
  int skipped = 0;
  for(int upstreamID = 0; upstreamID < upstreams; upstreamID++)
  {
- // Get upstream pointer
+ // Memory access needs to get locked
+ lock_shm();
+ // Get upstream pointer for the first time (reading data)
  upstreamsData* upstream = getUpstream(upstreamID, true);
  if(upstream == NULL)
  {
@@ -364,8 +378,6 @@ void resolveForwardDestinations(const bool onlynew)
  continue;
  }
 
- // Memory access needs to get locked
- lock_shm();
  bool newflag = upstream->new;
  size_t ippos = upstream->ippos;
  size_t oldnamepos = upstream->namepos;
@@ -383,6 +395,18 @@ void resolveForwardDestinations(const bool onlynew)
  size_t newnamepos = resolveAndAddHostname(ippos, oldnamepos);
 
  lock_shm();
+ // Get upstream pointer for the second time (writing data)
+ // We cannot use the same pointer again as we released
+ // the lock in between so we cannot know if something
+ // happened to the shared memory object (resize event)
+ upstream = getUpstream(upstreamID, true);
+ if(upstream == NULL)
+ {
+ logg("ERROR: Unable to get upstream pointer with ID %i, skipping...", upstreamID);
+ skipped++;
+ continue;
+ }
+
  // Store obtained host name (may be unchanged)
  upstream->namepos = newnamepos;
  // Mark entry as not new