From 772e8c23856e27960caba4dd87af42401b6c0cac Mon Sep 17 00:00:00 2001 From: Sean Quah <8349537+squahtx@users.noreply.github.com> Date: Fri, 13 Jan 2023 00:16:21 +0000 Subject: Fix stack overflow in `_PerHostRatelimiter` due to synchronous requests (#14812) When there are many synchronous requests waiting on a `_PerHostRatelimiter`, each request will be started recursively just after the previous request has completed. Under the right conditions, this leads to stack exhaustion. A common way for requests to become synchronous is when the remote client disconnects early, because the homeserver is overloaded and slow to respond. Avoid stack exhaustion under these conditions by deferring subsequent requests until the next reactor tick. Fixes #14480. Signed-off-by: Sean Quah --- synapse/rest/client/register.py | 1 + 1 file changed, 1 insertion(+) (limited to 'synapse/rest') diff --git a/synapse/rest/client/register.py b/synapse/rest/client/register.py index 3cb1e7e375..be696c304b 100644 --- a/synapse/rest/client/register.py +++ b/synapse/rest/client/register.py @@ -310,6 +310,7 @@ class UsernameAvailabilityRestServlet(RestServlet): self.hs = hs self.registration_handler = hs.get_registration_handler() self.ratelimiter = FederationRateLimiter( + hs.get_reactor(), hs.get_clock(), FederationRatelimitSettings( # Time window of 2s -- cgit 1.5.1