disconnect: separate connections and easy handles better

Do not assume/store assocation between a given easy handle and the
connection if it can be avoided.

Long-term, the 'conn->data' pointer should probably be removed as it is a
little too error-prone. Still used very widely though.

Reported-by: masbug on github
Fixes #3391
Closes #3400

1 files changed, 8 insertions, 2 deletions

diff --git a/lib/conncache.c b/lib/conncache.c
index 08e9042a6..080441854 100644
--- a/lib/conncache.c
+++ b/lib/conncache.c
@@ -302,9 +302,14 @@ CURLcode Curl_conncache_add_conn(struct conncache *connc,
   return result;
 }
 
-void Curl_conncache_remove_conn(struct connectdata *conn, bool lock)
+/*
+ * Removes the connectdata object from the connection cache *and* clears the
+ * ->data pointer association. Pass TRUE/FALSE in the 'lock' argument
+ * depending on if the parent function already holds the lock or not.
+ */
+void Curl_conncache_remove_conn(struct Curl_easy *data,
+                                struct connectdata *conn, bool lock)
 {
-  struct Curl_easy *data = conn->data;
   struct connectbundle *bundle = conn->bundle;
   struct conncache *connc = data->state.conn_cache;
 
@@ -323,6 +328,7 @@ void Curl_conncache_remove_conn(struct connectdata *conn, bool lock)
       DEBUGF(infof(data, "The cache now contains %zu members\n",
                    connc->num_conn));
     }
+    conn->data = NULL; /* clear the association */
     if(lock) {
       CONN_UNLOCK(data);
     }