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ext/session: fix session GC fork #22164

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ext/session: fix session GC fork #22164

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2 changes: 2 additions & 0 deletions ext/session/php_session.h
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Original file line number Diff line number Diff line change
Expand Up @@ -146,6 +146,8 @@ typedef struct _php_ps_globals {
zend_string *session_started_filename;
uint32_t session_started_lineno;
int module_number;
/* Unused since the GC probability draw was made stateless; retained only
* to preserve struct layout (ABI) on stable branches. */
php_random_status_state_pcgoneseq128xslrr64 random_state;
php_random_algo_with_state random;
zend_long gc_probability;
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23 changes: 8 additions & 15 deletions ext/session/session.c
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Original file line number Diff line number Diff line change
Expand Up @@ -392,9 +392,15 @@ static zend_long php_session_gc(bool immediate)

/* GC must be done before reading session data. */
if ((PS(mod_data) || PS(mod_user_implemented))) {
/* Use probability-based GC if not forced and probability is configured */
if (!collect && PS(gc_probability) > 0) {
collect = php_random_range(PS(random), 0, PS(gc_divisor) - 1) < PS(gc_probability);
/* Draw fresh entropy per request instead of using the per-process
* PS(random) state. The latter is seeded once in GINIT, which runs
* before SAPIs such as PHP-FPM fork their workers, so every worker
* would inherit and replay the same GC-decision sequence. */
uint32_t rand_val;
if (php_random_bytes_silent(&rand_val, sizeof(rand_val)) == SUCCESS) {
collect = (rand_val % (uint32_t) PS(gc_divisor)) < (uint32_t) PS(gc_probability);
}
}

if (collect) {
Expand Down Expand Up @@ -2886,19 +2892,6 @@ static PHP_GINIT_FUNCTION(ps)
ZVAL_UNDEF(&ps_globals->mod_user_names.ps_validate_sid);
ZVAL_UNDEF(&ps_globals->mod_user_names.ps_update_timestamp);
ZVAL_UNDEF(&ps_globals->http_session_vars);

ps_globals->random = (php_random_algo_with_state){
.algo = &php_random_algo_pcgoneseq128xslrr64,
.state = &ps_globals->random_state,
};
php_random_uint128_t seed;
if (php_random_bytes_silent(&seed, sizeof(seed)) == FAILURE) {
seed = php_random_uint128_constant(
php_random_generate_fallback_seed(),
php_random_generate_fallback_seed()
);
}
php_random_pcgoneseq128xslrr64_seed128(ps_globals->random.state, seed);
}

static PHP_MINIT_FUNCTION(session)
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