The purpose of dbus_get_proxies to construct the proxies corresponding to the
IDs registered to dbus-vmstate.

Currenty, this function returns an error in case there is any failure
while instantiating proxy for "all" the names on dbus.

Ideally this function should error out only if it is not able to find and
validate the proxies registered to the backend otherwise any offending
process(for eg: the process purposefully may not export its Id property on
the dbus) may connect to the dbus and can lead to migration failures.

This commit ensures that dbus_get_proxies returns an error if it is not
able to find and validate the proxies of interest(the IDs registered
during the dbus-vmstate instantiation).

Signed-off-by: Priyankar Jain <priyankar.jain@nutanix.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 backends/dbus-vmstate.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/backends/dbus-vmstate.c b/backends/dbus-vmstate.c
index 9cfd758c42..57369ec0f2 100644
--- a/backends/dbus-vmstate.c
+++ b/backends/dbus-vmstate.c
@@ -114,14 +114,19 @@ dbus_get_proxies(DBusVMState *self, GError **err)
                     "org.qemu.VMState1",
                     NULL, err);
         if (!proxy) {
-            return NULL;
+            if (err != NULL && *err != NULL) {
+                warn_report("%s: Failed to create proxy: %s",
+                            __func__, (*err)->message);
+                g_clear_error(err);
+            }
+            continue;
         }
 
         result = g_dbus_proxy_get_cached_property(proxy, "Id");
         if (!result) {
-            g_set_error_literal(err, G_IO_ERROR, G_IO_ERROR_FAILED,
-                                "VMState Id property is missing.");
-            return NULL;
+            warn_report("%s: VMState Id property is missing.", __func__);
+            g_clear_object(&proxy);
+            continue;
         }
 
         id = g_variant_dup_string(result, &size);
-- 
2.30.1 (Apple Git-130)

Hi Marc,
Could you please merge this in master? I see this commit is missing in 
master, although it was approved long back.

Thanks,
Priyankar Jain

On 26/11/21 7:45 pm, Priyankar Jain wrote:
> The purpose of dbus_get_proxies to construct the proxies corresponding to the
> IDs registered to dbus-vmstate.
> 
> Currenty, this function returns an error in case there is any failure
> while instantiating proxy for "all" the names on dbus.
> 
> Ideally this function should error out only if it is not able to find and
> validate the proxies registered to the backend otherwise any offending
> process(for eg: the process purposefully may not export its Id property on
> the dbus) may connect to the dbus and can lead to migration failures.
> 
> This commit ensures that dbus_get_proxies returns an error if it is not
> able to find and validate the proxies of interest(the IDs registered
> during the dbus-vmstate instantiation).
> 
> Signed-off-by: Priyankar Jain <priyankar.jain@nutanix.com>
> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
>   backends/dbus-vmstate.c | 13 +++++++++----
>   1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/backends/dbus-vmstate.c b/backends/dbus-vmstate.c
> index 9cfd758c42..57369ec0f2 100644
> --- a/backends/dbus-vmstate.c
> +++ b/backends/dbus-vmstate.c
> @@ -114,14 +114,19 @@ dbus_get_proxies(DBusVMState *self, GError **err)
>                       "org.qemu.VMState1",
>                       NULL, err);
>           if (!proxy) {
> -            return NULL;
> +            if (err != NULL && *err != NULL) {
> +                warn_report("%s: Failed to create proxy: %s",
> +                            __func__, (*err)->message);
> +                g_clear_error(err);
> +            }
> +            continue;
>           }
>   
>           result = g_dbus_proxy_get_cached_property(proxy, "Id");
>           if (!result) {
> -            g_set_error_literal(err, G_IO_ERROR, G_IO_ERROR_FAILED,
> -                                "VMState Id property is missing.");
> -            return NULL;
> +            warn_report("%s: VMState Id property is missing.", __func__);
> +            g_clear_object(&proxy);
> +            continue;
>           }
>   
>           id = g_variant_dup_string(result, &size);
>