53 lines
3.2 KiB
Markdown
53 lines
3.2 KiB
Markdown
---
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id: "bug-1917"
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status: "investigating"
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status_updated: "2026-10-03"
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status_note: "code-review finding from bug-1916; watch loaded soaks for reconnect stacks without free_packet"
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component: "lib"
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severity: "crash"
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timestamp: "2026-10-03T22:55:30Z"
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last_seen: "2026-10-03T22:55:30Z"
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occurrences: 1
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files: ["src/lib/xcectx.c", "src/lib/netio.c"]
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tags: ["race", "failover", "client", "ssl"]
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related: ["bug-1916"]
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---
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# bug-1917: xce_ctx_reconnect re-inits the endpoint on the caller thread while the io_worker may still use it
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## Description
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**Observed:**
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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.
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**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).
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**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.
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**Found by:** review (bug-1916 fix, 2026-10-03)
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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).
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## Environment
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- OS: no /etc/os-release; Docker container; NixOS kernel; kernel Linux 6.18.33 x86_64
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- libc: glibc 2.42-47 (interpreter /nix/store/wb6rhpznjfczwlwx23zmdrrw74bayxw4-glibc-2.42-47/lib/ld-linux-x86-64.so.2)
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- Toolchain: gcc (GCC) 15.2.0, meson 1.9.1
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- Build: asan (xce.build)
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- Code: scheduler-framework @ 6d9ef3d0-dirty
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- Deployment: any libxce client failing over during a controller failover (seen context: /xce-test-ha under 40 busy loops on 32 cores)
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## Reproduction
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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).
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- Frequency: 0/2 runs, 2026-10-03 (code-review finding; the 2 loaded soaks crashed on bug-1916 first)
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- Evidence: code reading of src/lib/xcectx.c xce_ctx_reconnect and src/lib/netio.c endpoint_fini / handle_input / handle_output
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## Root cause
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TODO: required for fixed/partial
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## Fix
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TODO: required for fixed/partial
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## Verification
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- Test: TODO: name + file; RED before the fix, GREEN after
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- Suites: TODO: suite results and build profile
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- Live: TODO: soak/deploy run, or n/a and why
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## References
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- Related: none
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