Change displayname of user as admin in rooms (matrix-org#6876)

changelog.d/6572.bugfix

@@ -0,0 +1 @@
+When a user's profile is updated via the admin API, also generate a displayname/avatar update for that user in each room.

synapse/handlers/profile.py

@@ -28,7 +28,7 @@
     SynapseError,
 )
 from synapse.metrics.background_process_metrics import run_as_background_process
-from synapse.types import UserID, get_domain_from_id
+from synapse.types import UserID, create_requester, get_domain_from_id
 
 from ._base import BaseHandler
 
@@ -165,6 +165,12 @@ def set_displayname(self, target_user, requester, new_displayname, by_admin=Fals
         if new_displayname == "":
             new_displayname = None
 
+        # If the admin changes the display name of a user, the requesting user cannot send
+        # the join event to update the displayname in the rooms.
+        # This must be done by the target user himself.
+        if by_admin:
+            requester = create_requester(target_user)
+
         yield self.store.set_profile_displayname(target_user.localpart, new_displayname)
 
         if self.hs.config.user_directory_search_all_users:
@@ -217,6 +223,10 @@ def set_avatar_url(self, target_user, requester, new_avatar_url, by_admin=False)
                 400, "Avatar URL is too long (max %i)" % (MAX_AVATAR_URL_LEN,)
             )
 
+        # Same like set_displayname
+        if by_admin:
+            requester = create_requester(target_user)
+
         yield self.store.set_profile_avatar_url(target_user.localpart, new_avatar_url)
 
         if self.hs.config.user_directory_search_all_users: