Segfault in `execute_ex`: `EX(run_time_cache)` is NULL for a trait-copied `private static` method (no opcache, no JIT)
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Description
Description
We are seeing a reproducible-in-aggregate segfault in the Zend VM on PHP 8.3.31
and 8.3.32 (Ubuntu 24.04, deb.sury.org builds, NTS). It occurs ~36 times/week on
one CI host under a Laravel application served by php -S (via
php artisan serve). Because the built-in server is a single process, each crash
takes the server down and every subsequent request is refused.
The engine executes an op_array whose run_time_cache is NULL, then performs a
run-time cache slot lookup against it.
Faulting instruction and registers, from a core dump (8.3.32):
=> execute_ex+15353: mov (%rdx,%rax,1),%rbx
rdx = 0x0 <- run-time cache base
rax = 0x8 <- cache slot offset
execute_ex+15357: test %rbx,%rbx
execute_ex+15360: je ...
Read directly from the core:
run_time_cache (execute_data + 0x40) = 0x0
Kernel log line (identical every time, same binary offset on every occurrence):
php8.3[3641252]: segfault at 8 ip ...2a3729 sp ... error 4 in php8.3[...+32f000]
error 4 = user-mode read of a non-present page; the faulting address is
literally 0 + 8, i.e. slot 1 of a NULL cache.
The function involved
Frame 0 is always the same PHP function, reached from different callers. Walking
execute_data out of the core (%r14; func at +0x18, prev_execute_data at
+0x30, function_name at +0x08, zend_string.val at +0x18):
#0 resolveTenantId <- always frame 0
#1 {closure} (an Eloquent global scope closure)
#2 {closure} -> callScope -> applyScopes
core A: ... -> get -> first -> resolveRouteBinding -> substituteImplicitBindings
core B: ... -> toBase -> __call -> currentAgencyHasStudio -> {closure}
resolveTenantId() is a private static method defined in a trait, and that
trait is used by ~68 classes — so the method exists as ~68 separate op_arrays,
each with its own ZEND_MAP_PTR run-time cache. It is called on a very hot path
(every scoped query). Its body is small:
private static function resolveTenantId(): int|string|null
{
if (! function_exists('app')) {
return null;
}
$resolver = app()->bound(TenantResolver::class)
? app(TenantResolver::class)
: null;
return $resolver?->currentTenantId();
}
Ruled out
- opcache / JIT —
opcache.enable_cli => Off. opcache.so is loaded as a
module but caches nothing in this SAPI; JIT therefore never engages. (This
distinguishes it from #22158, which is JIT-specific, and #9396, which requires
opcache.) PHP_CLI_SERVER_WORKERS— unset; confirmed absent from the core's
environment, so the experimental forking server is not involved.- pcov / xdebug or any other VM-hooking extension — not among the 65
extensions loaded in the crashed process. - Userland recursion into the same scope — the class queried by the resolver
is exempt from the global scope, so there is no re-entry loop. - PHP 8.3.33 — its NEWS contains only Date/GD/PGSQL/Phar entries; nothing
engine-related, so we do not expect it to change this.
Environment
- PHP 8.3.32 (
8.3.32-1+ubuntu24.04.1+deb.sury.org+1) and 8.3.31, both NTS, both
affected, on two separate hosts - Ubuntu 24.04
- SAPI:
cli-server(php -S) - opcache loaded,
opcache.enable_cli=Off, JIT inactive - 65 extensions loaded
What I have and what I don't
I have core dumps and can extract any additional structure from them on request
(op_array fields, the zend_function at execute_data+0x18, the opline, etc.).
I do not have a minimal reproducer, and I have tried. The crash is frequent
in aggregate (~5/day) but not deterministic per-request, which is consistent with
an allocation- or lifetime-related issue around the run-time cache rather than a
specific input.
Attempts, both run on the same affected binary and host, both negative:
- Structural mimic — one trait with a
private staticmethod calling
function_exists(), a container-ish helper and a nullsafe method call; 68
classes using the trait; each invoked through astatic functionclosure via
call_user_func(to mirror the global-scope indirection); served by
php -S. 400 requests, ~186k calls: no crash. - Same, scaled to 1500 trait-using classes + 1500 free functions to force
ZEND_MAP_PTRtable growth and reallocation across a long-lived
php -Sprocess. 500 requests: no crash.
So the trait-copy structure alone is not sufficient. Something else in the real
workload is required — plausibly overall arena/memory pressure, the volume of
classes autoloaded per request, or live PDO/session activity. I mention the
negative results explicitly so nobody re-runs the same experiment.
I have the core dumps and can extract any additional structure from them on
request, or run a diagnostic/assertion build against the live workload — that is
likely the fastest route to a fix, since the workload reproduces it reliably in
aggregate even though a reduced case does not.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start at the execute_ex fault and inspect execute_data, the op_array, and the NULL run_time_cache described in the core dumps. Use a diagnostic or assertion build against the affected php -S workload, and compare the trait-copied private static method's runtime-cache state across calls. Done means reproducing the invalid cache access and identifying a confirmed engine-level cause and regression test or fix.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- c, php
- Domain
- backend, compilers
- Issue type
- Bug
- Difficulty
- 5/5
- Estimated time
- Over a week
- Activity status
- Quiet
- Clarity
- Needs clarification
- Newbie friendliness
- 25/100