http2: Fix crashes when parent stream gets aborted

Closes #1125

lib/http2.c

@@ -2108,6 +2108,82 @@ CURLcode Curl_http2_switched(struct connectdata *conn,
   return CURLE_OK;
 }
 
+void Curl_http2_add_child(struct Curl_easy *parent, struct Curl_easy *child,
+                          bool exclusive)
+{
+  struct Curl_http2_dep **tail;
+  struct Curl_http2_dep *dep = calloc(1, sizeof(struct Curl_http2_dep));
+  dep->data = child;
+
+  if(parent->set.stream_dependents && exclusive) {
+    struct Curl_http2_dep *node = parent->set.stream_dependents;
+    while(node) {
+      node->data->set.stream_depends_on = child;
+      node = node->next;
+    }
+
+    tail = &child->set.stream_dependents;
+    while(*tail)
+      tail = &(*tail)->next;
+
+    DEBUGASSERT(!*tail);
+    *tail = parent->set.stream_dependents;
+    parent->set.stream_dependents = 0;
+  }
+
+  tail = &parent->set.stream_dependents;
+  while(*tail) {
+    (*tail)->data->set.stream_depends_e = FALSE;
+    tail = &(*tail)->next;
+  }
+
+  DEBUGASSERT(!*tail);
+  *tail = dep;
+
+  child->set.stream_depends_on = parent;
+  child->set.stream_depends_e = exclusive;
+}
+
+void Curl_http2_remove_child(struct Curl_easy *parent, struct Curl_easy *child)
+{
+  struct Curl_http2_dep *last = 0;
+  struct Curl_http2_dep *data = parent->set.stream_dependents;
+  DEBUGASSERT(child->set.stream_depends_on == parent);
+
+  while(data && data->data != child) {
+    last = data;
+    data = data->next;
+  }
+
+  DEBUGASSERT(data);
+
+  if(data) {
+    if(last) {
+      last->next = data->next;
+    }
+    else {
+      parent->set.stream_dependents = data->next;
+    }
+    free(data);
+  }
+
+  child->set.stream_depends_on = 0;
+  child->set.stream_depends_e = FALSE;
+}
+
+void Curl_http2_cleanup_dependencies(struct Curl_easy *data)
+{
+  while(data->set.stream_dependents) {
+    struct Curl_easy *tmp = data->set.stream_dependents->data;
+    Curl_http2_remove_child(data, tmp);
+    if(data->set.stream_depends_on)
+      Curl_http2_add_child(data->set.stream_depends_on, tmp, FALSE);
+  }
+
+  if(data->set.stream_depends_on)
+    Curl_http2_remove_child(data->set.stream_depends_on, data);
+}
+
 #else /* !USE_NGHTTP2 */
 
 /* Satisfy external references even if http2 is not compiled in. */

lib/http2.h

@@ -53,6 +53,11 @@ void Curl_http2_setup_conn(struct connectdata *conn);
 void Curl_http2_setup_req(struct Curl_easy *data);
 void Curl_http2_done(struct connectdata *conn, bool premature);
 CURLcode Curl_http2_done_sending(struct connectdata *conn);
+void Curl_http2_add_child(struct Curl_easy *parent, struct Curl_easy *child,
+                          bool exclusive);
+void Curl_http2_remove_child(struct Curl_easy *parent,
+                             struct Curl_easy *child);
+void Curl_http2_cleanup_dependencies(struct Curl_easy *data);
 #else /* USE_NGHTTP2 */
 #define Curl_http2_init(x) CURLE_UNSUPPORTED_PROTOCOL
 #define Curl_http2_send_request(x) CURLE_UNSUPPORTED_PROTOCOL
@@ -65,6 +70,9 @@ CURLcode Curl_http2_done_sending(struct connectdata *conn);
 #define Curl_http2_init_userset(x)
 #define Curl_http2_done(x,y)
 #define Curl_http2_done_sending(x)
+#define Curl_http2_add_child(x, y, z)
+#define Curl_http2_remove_child(x, y)
+#define Curl_http2_cleanup_dependencies(x)
 #endif
 
 #endif /* HEADER_CURL_HTTP2_H */

lib/url.c

@@ -464,6 +464,7 @@ CURLcode Curl_close(struct Curl_easy *data)
   /* this destroys the channel and we cannot use it anymore after this */
   Curl_resolver_cleanup(data->state.resolver);
 
+  Curl_http2_cleanup_dependencies(data);
   Curl_convert_close(data);
 
   /* No longer a dirty share, if it exists */
@@ -2847,9 +2848,11 @@ CURLcode Curl_setopt(struct Curl_easy *data, CURLoption option,
     return CURLE_NOT_BUILT_IN;
 #else
     struct Curl_easy *dep = va_arg(param, struct Curl_easy *);
-    if(dep && GOOD_EASY_HANDLE(dep)) {
-      data->set.stream_depends_on = dep;
-      data->set.stream_depends_e = (option == CURLOPT_STREAM_DEPENDS_E);
+    if(!dep || GOOD_EASY_HANDLE(dep)) {
+      if(data->set.stream_depends_on) {
+        Curl_http2_remove_child(data->set.stream_depends_on, data);
+      }
+      Curl_http2_add_child(dep, data, (option == CURLOPT_STREAM_DEPENDS_E));
     }
     break;
 #endif

lib/urldata.h

@@ -1280,6 +1280,11 @@ struct auth {
                    be RFC compliant */
 };
 
+struct Curl_http2_dep {
+  struct Curl_http2_dep *next;
+  struct Curl_easy *data;
+};
+
 struct UrlState {
 
   /* Points to the connection cache */
@@ -1747,6 +1752,8 @@ struct UserDefined {
   struct Curl_easy *stream_depends_on;
   bool stream_depends_e; /* set or don't set the Exclusive bit */
   int stream_weight;
+
+  struct Curl_http2_dep *stream_dependents;
 };
 
 struct Names {