From b95407908dfde97e483952722b6fa7a533ff5093 Mon Sep 17 00:00:00 2001
From: Sean Quah <8349537+squahtx@users.noreply.github.com>
Date: Fri, 10 Feb 2023 13:11:20 +0000
Subject: [PATCH] Avoid mutating cached values in
 `_generate_sync_entry_for_account_data` (#15047)

---
 changelog.d/15047.misc   | 1 +
 synapse/handlers/sync.py | 2 ++
 2 files changed, 3 insertions(+)
 create mode 100644 changelog.d/15047.misc

diff --git a/changelog.d/15047.misc b/changelog.d/15047.misc
new file mode 100644
index 000000000000..561dc874de0e
--- /dev/null
+++ b/changelog.d/15047.misc
@@ -0,0 +1 @@
+Avoid mutating cached values in `_generate_sync_entry_for_account_data`.
diff --git a/synapse/handlers/sync.py b/synapse/handlers/sync.py
index 3566537894e6..202b35eee6d3 100644
--- a/synapse/handlers/sync.py
+++ b/synapse/handlers/sync.py
@@ -1753,6 +1753,7 @@ async def _generate_sync_entry_for_account_data(
             )
 
             if push_rules_changed:
+                global_account_data = dict(global_account_data)
                 global_account_data["m.push_rules"] = await self.push_rules_for_user(
                     sync_config.user
                 )
@@ -1763,6 +1764,7 @@ async def _generate_sync_entry_for_account_data(
                 account_data_by_room,
             ) = await self.store.get_account_data_for_user(sync_config.user.to_string())
 
+            global_account_data = dict(global_account_data)
             global_account_data["m.push_rules"] = await self.push_rules_for_user(
                 sync_config.user
             )