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authorSean Quah <8349537+squahtx@users.noreply.github.com>2023-01-13 00:16:21 +0000
committerGitHub <noreply@github.com>2023-01-13 00:16:21 +0000
commit772e8c23856e27960caba4dd87af42401b6c0cac (patch)
tree11d8c1cb6bb8780277d4caa5d67bb2334b0222f4 /synapse/rest
parentMerge branch 'release-v1.75' into develop (diff)
downloadsynapse-772e8c23856e27960caba4dd87af42401b6c0cac.tar.xz
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 <seanq@matrix.org>
Diffstat (limited to 'synapse/rest')
-rw-r--r--synapse/rest/client/register.py1
1 files changed, 1 insertions, 0 deletions
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