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>

diff --git a/tools/xenstore/xenstored_core.c b/tools/xenstore/xenstored_core.c
index 6002cad3c46e115a1e99c4faac4fdc7107473077..fcc37983288d9ab3f0e7556d6b724ebebfd0b3db 100644 (file)
--- a/tools/xenstore/xenstored_core.c
+++ b/tools/xenstore/xenstored_core.c
@@ -1118,8 +1118,8 @@ static void delete_child(struct connection *conn,
        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;
 
@@ -1131,7 +1131,7 @@ static int delete_node(struct connection *conn, struct node *parent,
                                       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",
@@ -1143,6 +1143,7 @@ static int delete_node(struct connection *conn, struct node *parent,
                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);
@@ -1172,8 +1173,8 @@ static int _rm(struct connection *conn, const void *ctx, struct node *node,
         * 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);
 }
 
 

diff --git a/tools/xenstore/xenstored_watch.c b/tools/xenstore/xenstored_watch.c
index cc82864a6e7e814f04822c498eb8820f2b0e297d..7ca18e03488ce3c7cbcb18288ce8c70308c5ff58 100644 (file)
--- a/tools/xenstore/xenstored_watch.c
+++ b/tools/xenstore/xenstored_watch.c
@@ -122,7 +122,7 @@ static void add_event(struct connection *conn,
  * 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;
@@ -134,10 +134,13 @@ void fire_watches(struct connection *conn, const void *ctx, const char *name,
        /* 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);
+                       }
                }
        }
 }

diff --git a/tools/xenstore/xenstored_watch.h b/tools/xenstore/xenstored_watch.h
index 54d4ea7e0d418f8c5602d4417d4434e302081ad8..1b3c80d3dda110f99f5173c958e44ecebd825727 100644 (file)
--- a/tools/xenstore/xenstored_watch.h
+++ b/tools/xenstore/xenstored_watch.h
@@ -24,9 +24,9 @@
 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);