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

[Paolo Bonzini <pbonzini@redhat.com>]

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