## Summary
The diagnostic loop in `mod_init()` at
[tls_mod.c:413](https://github.com/kamailio/kamailio/blob/6.1.1/src/modules/tls/tls_mod.c#L413)
calls `pthread_getspecific()` with raw integer keys 0–31. On musl libc (Alpine
Linux), the main thread's pthread TSD array (`self->tsd`) is `NULL`
until `pthread_key_create()` is called at least once, so
`pthread_getspecific()` dereferences a NULL pointer → segfault.
This loop runs unconditionally before any `tls_threads_mode` or `tls_disable`
check, so no configuration setting can prevent the crash.
### Fix
Create and immediately delete a pthread key before the diagnostic loop to force
TSD initialization. This is a no-op on glibc and resolves the crash on musl.
### Reproduction
```
docker run --rm --entrypoint sh ghcr.io/kamailio/kamailio-ci:6.1.1-alpine -c
'
cat > /tmp/tls_test.cfg << "CFGEOF"
enable_tls = 1
tcp_main_threads = 1
loadmodule "sl.so"
loadmodule "tm.so"
loadmodule "tls.so"
listen=tls:0.0.0.0:5061
request_route {
sl_send_reply("200", "OK");
}
CFGEOF
kamailio -f /tmp/tls_test.cfg -DD -E; echo "EXIT CODE: $?"'
```
Output: `EXIT CODE: 139` (SIGSEGV)
### References
- kamailio/kamailio-ci#20
- #4534
- [musl mailing list
analysis](https://www.openwall.com/lists/musl/2025/12/21/2) — Rich Felker (musl
author) confirms iterating raw integers through `pthread_getspecific` is
undefined behavior
Made with [Cursor](https://cursor.com)
You can view, comment on, or merge this pull request online at:
https://github.com/kamailio/kamailio/pull/4628
-- Commit Summary --
* tls: fix segfault on musl libc due to uninitialized pthread TSD
-- File Changes --
M src/modules/tls/tls_mod.c (5)
-- Patch Links --
https://github.com/kamailio/kamailio/pull/4628.patch
https://github.com/kamailio/kamailio/pull/4628.diff
--
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