From 6ca2e14b43aecc79effc1a0cd528a4aceef44d42 Mon Sep 17 00:00:00 2001
From: Juergen Gross <jgross@suse.com>
Date: Thu, 11 Jun 2020 16:12:43 +0200
Subject: [PATCH 07/10] tools/xenstore: fire watches only when removing a
 specific node

Instead of firing all watches for removing a subtree in one go, do so
only when the related node is being removed.

The watches for the top-most node being removed include all watches
including that node, while watches for nodes below that are only fired
if they are matching exactly. This avoids firing any watch more than
once when removing a subtree.

This is part of XSA-115.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Paul Durrant <paul@xen.org>
---
 tools/xenstore/xenstored_core.c  | 11 ++++++-----
 tools/xenstore/xenstored_watch.c | 13 ++++++++-----
 tools/xenstore/xenstored_watch.h |  4 ++--
 3 files changed, 16 insertions(+), 12 deletions(-)

Index: xen-4.0.3-testing/tools/xenstore/xenstored_core.c
===================================================================
--- xen-4.0.3-testing.orig/tools/xenstore/xenstored_core.c
+++ xen-4.0.3-testing/tools/xenstore/xenstored_core.c
@@ -1087,8 +1087,8 @@ static void delete_child(struct connecti
 	corrupt(conn, "Can't find child '%s' in %s", childname, node->name);
 }
 
-static int delete_node(struct connection *conn, struct node *parent,
-		       struct node *node)
+static int delete_node(struct connection *conn, const void *ctx,
+		       struct node *parent, struct node *node)
 {
 	char *name;
 
@@ -1100,7 +1100,7 @@ static int delete_node(struct connection
 				       node->children);
 		child = name ? read_node(conn, node, name) : NULL;
 		if (child) {
-			if (delete_node(conn, node, child))
+			if (delete_node(conn, ctx, node, child))
 				return errno;
 		} else {
 			trace("delete_node: Error deleting child '%s/%s'!\n",
@@ -1112,6 +1112,7 @@ static int delete_node(struct connection
 		talloc_free(name);
 	}
 
+	fire_watches(conn, ctx, node->name, true);
 	delete_node_single(conn, node);
 	delete_child(conn, parent, basename(node->name));
 	talloc_free(node);
@@ -1141,8 +1142,8 @@ static int _rm(struct connection *conn,
 	 * This fine as we are single threaded and the next possible read will
 	 * be handled only after the node has been really removed.
 	 */
-	fire_watches(conn, ctx, name, true);
-	return delete_node(conn, parent, node);
+	fire_watches(conn, ctx, name, false);
+	return delete_node(conn, ctx, parent, node);
 }
 
 
Index: xen-4.0.3-testing/tools/xenstore/xenstored_watch.c
===================================================================
--- xen-4.0.3-testing.orig/tools/xenstore/xenstored_watch.c
+++ xen-4.0.3-testing/tools/xenstore/xenstored_watch.c
@@ -123,7 +123,7 @@ static void add_event(struct connection
  * Temporary memory allocations are done with ctx.
  */
 void fire_watches(struct connection *conn, const void *ctx, const char *name,
-		  bool recurse)
+		  bool exact)
 {
 	struct connection *i;
 	struct watch *watch;
@@ -135,10 +135,13 @@ void fire_watches(struct connection *con
 	/* Create an event for each watch. */
 	list_for_each_entry(i, &connections, list) {
 		list_for_each_entry(watch, &i->watches, list) {
-			if (is_child(name, watch->node))
-				add_event(i, ctx, watch, name);
-			else if (recurse && is_child(watch->node, name))
-				add_event(i, ctx, watch, watch->node);
+			if (exact) {
+				if (streq(name, watch->node))
+					add_event(i, ctx, watch, name);
+			} else {
+				if (is_child(name, watch->node))
+					add_event(i, ctx, watch, name);
+			}
 		}
 	}
 }
Index: xen-4.0.3-testing/tools/xenstore/xenstored_watch.h
===================================================================
--- xen-4.0.3-testing.orig/tools/xenstore/xenstored_watch.h
+++ xen-4.0.3-testing/tools/xenstore/xenstored_watch.h
@@ -25,9 +25,9 @@
 int do_watch(struct connection *conn, struct buffered_data *in);
 int do_unwatch(struct connection *conn, struct buffered_data *in);
 
-/* Fire all watches: recurse means all the children are affected (ie. rm). */
+/* Fire all watches: !exact means all the children are affected (ie. rm). */
 void fire_watches(struct connection *conn, const void *tmp, const char *name,
-		  bool recurse);
+		  bool exact);
 
 void conn_delete_all_watches(struct connection *conn);
 
