Add a rend cache failure info dup function

When validating a new descriptor against our rend cache failure, we were
added the failure entry to the new cache entry without duplicating. It was
then freed just after the validation ending up in a very bad memory state
that was making tor abort(). To fix this, a dup function has been added and
used just before adding the failure entry.

Fixes #17041

Signed-off-by: David Goulet <dgoulet@ev0ke.net>

src/or/rendcache.c

@@ -334,6 +334,17 @@ cache_failure_intro_lookup(const uint8_t *identity, const char *service_id,
   return 0;
 }
 
+/** Allocate a new cache failure intro object and copy the content from
+ * <b>entry</b> to this newly allocated object. Return it. */
+static rend_cache_failure_intro_t *
+cache_failure_intro_dup(const rend_cache_failure_intro_t *entry)
+{
+  rend_cache_failure_intro_t *ent_dup =
+    rend_cache_failure_intro_entry_new(entry->failure_type);
+  ent_dup->created_ts = entry->created_ts;
+  return ent_dup;
+}
+
 /** Add an intro point failure to the failure cache using the relay
  * <b>identity</b> and service ID <b>service_id</b>. Record the
  * <b>failure</b> in that object. */
@@ -383,12 +394,15 @@ validate_intro_point_failure(const rend_service_descriptor_t *desc,
 
     found = cache_failure_intro_lookup(identity, service_id, &entry);
     if (found) {
+      /* Dup here since it will be freed at the end when removing the
+       * original entry in the cache. */
+      rend_cache_failure_intro_t *ent_dup = cache_failure_intro_dup(entry);
       /* This intro point is in our cache, discard it from the descriptor
        * because chances are that it's unusable. */
       SMARTLIST_DEL_CURRENT(desc->intro_nodes, intro);
       rend_intro_point_free(intro);
       /* Keep it for our new entry. */
-      digestmap_set(new_entry->intro_failures, (char *) identity, entry);
+      digestmap_set(new_entry->intro_failures, (char *) identity, ent_dup);
       continue;
     }
   } SMARTLIST_FOREACH_END(intro);