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Re: [PATCH] monitor: Fix find_device_state() for IDs containing slashes


From: Paolo Bonzini
Subject: Re: [PATCH] monitor: Fix find_device_state() for IDs containing slashes
Date: Tue, 19 Oct 2021 12:13:08 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.1.0

On 19/10/21 10:57, Markus Armbruster wrote:
Recent commit 6952026120 "monitor: Tidy up find_device_state()"
assumed the function's argument is "the device's ID or QOM path" (as
documented for device_del).  It's actually either an absolute QOM
path, or a QOM path relative to /machine/peripheral/.  Such a relative
path is a device ID when it doesn't contain a slash.  When it does,
the function now always fails.  Broke iotest 200, which uses relative
path "vda/virtio-backend".

It fails because object_resolve_path_component() resolves just one
component, not a relative path.

The obvious function to resolve relative paths is
object_resolve_path().  It picks a parent automatically.  Too much
magic, we want to specify the parent.  Create new
object_resolve_path_at() for that, and use it in find_device_state().

Reported-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
  include/qom/object.h   | 12 ++++++++++++
  qom/object.c           | 11 +++++++++++
  softmmu/qdev-monitor.c |  8 +-------
  3 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/include/qom/object.h b/include/qom/object.h
index faae0d841f..fae096f51c 100644
--- a/include/qom/object.h
+++ b/include/qom/object.h
@@ -1543,6 +1543,18 @@ Object *object_resolve_path(const char *path, bool 
*ambiguous);
  Object *object_resolve_path_type(const char *path, const char *typename,
                                   bool *ambiguous);
+/**
+ * object_resolve_path_at:
+ * @parent: the object in which to resolve the path
+ * @path: the path to resolve
+ *
+ * This is like object_resolve_path(), except paths not starting with
+ * a slash are relative to @parent.
+ *
+ * Returns: The resolved object or NULL on path lookup failure.
+ */
+Object *object_resolve_path_at(Object *parent, const char *path);
+
  /**
   * object_resolve_path_component:
   * @parent: the object in which to resolve the path
diff --git a/qom/object.c b/qom/object.c
index 6be710bc40..4f0677cca9 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -2144,6 +2144,17 @@ Object *object_resolve_path(const char *path, bool 
*ambiguous)
      return object_resolve_path_type(path, TYPE_OBJECT, ambiguous);
  }
+Object *object_resolve_path_at(Object *parent, const char *path)
+{
+    g_auto(GStrv) parts = g_strsplit(path, "/", 0);
+
+    if (*path == '/') {
+        return object_resolve_abs_path(object_get_root(), parts + 1,
+                                       TYPE_OBJECT);
+    }
+    return object_resolve_abs_path(parent, parts, TYPE_OBJECT);
+}
+
  typedef struct StringProperty
  {
      char *(*get)(Object *, Error **);
diff --git a/softmmu/qdev-monitor.c b/softmmu/qdev-monitor.c
index 89c473cb22..e8a1c7e52a 100644
--- a/softmmu/qdev-monitor.c
+++ b/softmmu/qdev-monitor.c
@@ -865,15 +865,9 @@ void qmp_device_add(QDict *qdict, QObject **ret_data, 
Error **errp)
static DeviceState *find_device_state(const char *id, Error **errp)
  {
-    Object *obj;
+    Object *obj = object_resolve_path_at(qdev_get_peripheral(), id);
      DeviceState *dev;
- if (id[0] == '/') {
-        obj = object_resolve_path(id, NULL);
-    } else {
-        obj = object_resolve_path_component(qdev_get_peripheral(), id);
-    }
-
      if (!obj) {
          error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND,
                    "Device '%s' not found", id);


Acked-by: Paolo Bonzini <pbonzini@redhat.com>

Thanks for the quick fix!

Paolo




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