redis: fix use-after-free on overlapping cluster discovery refresh#45902
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redis: fix use-after-free on overlapping cluster discovery refresh#45902mateenali66 wants to merge 2 commits into
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CLUSTER SLOTS clears current_request_ as soon as it completes, while the zone-discovery INFO requests it triggers are still in flight. A refresh (periodic resolve timer or DNS update) arriving in that window re-entered startResolveRedis(), started a second zone discovery and overwrote zone_callbacks_, freeing the callbacks that the in-flight INFO requests still referenced. Gate startResolveRedis() on pending_zone_requests_ so a refresh is skipped until zone discovery finishes, and add a regression test. Signed-off-by: Mateen Anjum <mateenali66@gmail.com>
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The changelog fragment area must match the canonical set in changelogs/changelogs.yaml; the Redis subsystem area is redis_proxy, not redis. Signed-off-by: Mateen Anjum <mateenali66@gmail.com>
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Jul 2, 2026
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Fix a use-after-free in the Redis cluster CLUSTER SLOTS discovery. current_request_ is cleared as soon as CLUSTER SLOTS completes, while the zone-discovery INFO requests it triggers are still in flight. A refresh (periodic resolve timer or DNS update) arriving in that window re-entered startResolveRedis(), started a second zone discovery and overwrote zone_callbacks_, freeing the callbacks that the in-flight INFO requests still referenced. Gate startResolveRedis() on pending_zone_requests_ so a refresh is skipped until zone discovery finishes.
Additional Description: startResolveRedis() guarded re-entry only on current_request_, which onResponse() clears the moment CLUSTER SLOTS completes. The INFO requests started by startZoneDiscovery() are still outstanding at that point (tracked by the existing pending_zone_requests_ counter), so an external refresh in the gap passed the guard, ran startZoneDiscovery() again and overwrote zone_callbacks_[addr], freeing the ZoneDiscoveryCallback that an in-flight ClientImpl::PendingRequest still holds by reference. Adds a second early-return guard on pending_zone_requests_. Fixes #45870.
Risk Level: Low (adds an early-return guard in the discovery re-entry path; the normal first-resolution and steady-state paths are unchanged).
Testing: Added unit regression test ZoneDiscoveryRefreshWhileInfoInFlightIsSkipped in test/extensions/clusters/redis/redis_cluster_test.cc: it fires the resolve timer while zone-discovery INFO requests are in flight and asserts no second CLUSTER SLOTS request is issued, then completes discovery normally. Run: ./ci/do_ci.sh debug //test/extensions/clusters/redis:redis_cluster_test
Docs Changes: N/A
Release Notes: changelogs/current/bug_fixes/redis__zone-discovery-use-after-free.rst
I have reviewed and understand all of the submitted code.