---
id: "bug-1917"
status: "investigating"
status_updated: "2026-10-03"
status_note: "code-review finding from bug-1916; watch loaded soaks for reconnect stacks without free_packet"
component: "lib"
severity: "crash"
timestamp: "2026-10-03T22:55:30Z"
last_seen: "2026-10-03T22:55:30Z"
occurrences: 1
files: ["src/lib/xcectx.c", "src/lib/netio.c"]
tags: ["race", "failover", "client", "ssl"]
related: ["bug-1916"]
---

# bug-1917: xce_ctx_reconnect re-inits the endpoint on the caller thread while the io_worker may still use it

## Description
**Observed:**
Not yet observed as a crash -- found by code review while fixing bug-1916. `xce_ctx_reconnect` (src/lib/xcectx.c ~366) calls `endpoint_fini` / `endpoint_init` on the client's caller thread for an endpoint embedded in the context, while the io_worker may still be dispatching the same endpoint (still monitored). Exposed operations: the io_worker's post-handler store into `ep->fsm_in.pkt` and `endpoint_unref` (harmless after the bug-1916 fix), a concurrent `SSL_read` / `handle_error` on the old fd/SSL against `SSL_free` / `close`, and `fsm_out.pkt` freed while `handle_output` is writing it. `vtask_entry` also reads `ep->owner` without a lock while reconnect rewrites it.

**Expected:** reconnect first unmonitors the old endpoint and waits for the io_worker to finish any in-flight dispatch on it (quiesce), then tears it down, as the controller side does with deferred per-endpoint teardown (bug-1839).
**Impact:** potential use-after-free / crash in OpenSSL or `handle_output` stacks under `xce_ctx_reconnect` during client failover (worker, scheduler, xce_test, apiserver backend), most likely under heavy CPU load, like bug-1916.
**Found by:** review (bug-1916 fix, 2026-10-03)

UPDATE (2026-10-03): Review of the bug-1916 fix (2026-10-03) adds a second hazard: a reply task from the OLD connection still queued when xce_ctx_reconnect re-arms ep->owner can run against the NEW session (ep->owner read unsynchronised in xcectx.c vtask_entry ~134-135).

## Environment
- OS: no /etc/os-release; Docker container; NixOS kernel; kernel Linux 6.18.33 x86_64
- libc: glibc 2.42-47 (interpreter /nix/store/wb6rhpznjfczwlwx23zmdrrw74bayxw4-glibc-2.42-47/lib/ld-linux-x86-64.so.2)
- Toolchain: gcc (GCC) 15.2.0, meson 1.9.1
- Build: asan (xce.build)
- Code: scheduler-framework @ 6d9ef3d0-dirty
- Deployment: any libxce client failing over during a controller failover (seen context: /xce-test-ha under 40 busy loops on 32 cores)

## Reproduction
1. Not reproduced yet. Candidate: loaded `/xce-test-ha` soaks (40 busy loops on 32 cores) with the bug-1916 fix in place; look for ASAN reports with `xce_ctx_reconnect` in the stack but not `free_packet` (e.g. SSL_read/SSL_free or handle_output frames).
- Frequency: 0/2 runs, 2026-10-03 (code-review finding; the 2 loaded soaks crashed on bug-1916 first)
- Evidence: code reading of src/lib/xcectx.c xce_ctx_reconnect and src/lib/netio.c endpoint_fini / handle_input / handle_output

## Root cause
TODO: required for fixed/partial

## Fix
TODO: required for fixed/partial

## Verification
- Test: TODO: name + file; RED before the fix, GREEN after
- Suites: TODO: suite results and build profile
- Live: TODO: soak/deploy run, or n/a and why

## References
- Related: none