---
id: "bug-1600"
status: "fixed"
status_updated: "2026-09-24"
status_note: "ddee884c"
component: "lib"
severity: "crash"
timestamp: "2026-08-19T21:05:00Z"
last_seen: "2026-09-19T09:00:00Z"
occurrences: 8
files: ["src/lib/group.c"]
tags: ["scheduler", "crash", "sigabrt", "heap-corruption", "bad-free", "allocator-mismatch", "rtti", "makeString", "group.c", "config-push", "failover", "production"]
related: ["bug-1503"]
fix_commits: ["ddee884c"]
legacy: true
---

# bug-1600: xce_scheduler crashed with free(): invalid pointer / ASAN bad-free during controller failover…

## Description
xce_scheduler crashed with free(): invalid pointer / ASAN bad-free during controller failover retry (3x config-push retry loop); 6 crash-loop occurrences on 2026-08-17, 2 more on 2026-08-19 (core dumps confirmed via gdb bt full and coredumpctl, crash site consistently makeGroup() at src/lib/group.c:234)

## Environment
_Not recorded (migrated from buglog.json)._

## Reproduction
_Not recorded (migrated from buglog.json)._

## Root cause
makeGroup() existing-group update path (the branch taken when a config-push re-applies a group name that already exists, e.g. every retried/duplicate config push) freed xce_g_member_t.u.name via FREEUP() (raw free()). u.name is allocated by makeString() (make_g_member(), group.c:77), an rtti-managed pointer returned by makeInstance()/objAlloc() that is NOT the malloc()-returned base address (it is an offset into a combined header+data block) and is refcounted, not malloc-owned. Calling free() on it is undefined behavior -> heap corruption, surfacing later as glibc/ASAN bad-free aborts on unrelated allocations. group_killer() (same file) already released the identical field correctly via dereference(). The buggy FREEUP() path is hit on every config re-push for a group with existing members (e.g. controller failover retrying a config push), which explains the crash correlating with the 3-attempt xcecli_retry_next() failover loop even though no thread concurrency is required to trigger it.

## Fix
Changed both FREEUP(m->u.name) call sites inside makeGroup()'s existing-group branch (group.c, the g->members loop and the g->ex_members loop) to dereference(m->u.name), matching group_killer()'s established correct pattern for releasing rtti makeString() pointers. Added regression test test_reconfigure_same_group_members (src/lib/testsuite/test_group.c) that calls makeGroup() twice with the same group name/members, reproducing the exact ASAN bad-free at group.c:234 pre-fix (confirmed RED), and passing clean post-fix (confirmed GREEN, full lib asan suite Ok:1 Fail:0, no regressions). NOTE: a separate, related latent issue was also found but NOT fixed here (out of scope, no concurrency needed to explain the observed crash) - the entire existing-group update branch in makeGroup() only takes RTTI_LOCK_READ (a genuine shared pthread_rwlock_rdlock) while mutating shared group state, and sched_init_config()/plugin_config_update() (the config-push handler chain) hold no serializing lock at all, so two vtask worker threads (scheduler runs a 4-vcpu pool) could in principle race on the same group concurrently -- most plausibly triggered by xce_ctx_reconnect() reusing the same endpoint struct and endpoint_init() resetting ep->busy=0 before an already-dispatched handler finishes. This should be tracked as a follow-up.

## Verification
_Not recorded (migrated from buglog.json)._

## References
- Related: bug-1503