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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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5a58ed1
fix: session GC fork
jorgsowa May 27, 2026
b51f15e
fix: seed session GC RNG lazily per worker process
jorgsowa Jun 10, 2026
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1 change: 1 addition & 0 deletions ext/session/php_session.h
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Original file line number Diff line number Diff line change
Expand Up @@ -203,6 +203,7 @@ typedef struct _php_ps_globals {
bool in_save_handler; /* state if session is in save handler or not */
bool set_handler; /* state if session module i setting handler or not */
zend_string *session_vars; /* serialized original session data */
bool random_seeded;
} php_ps_globals;

typedef php_ps_globals zend_ps_globals;
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21 changes: 13 additions & 8 deletions ext/session/session.c
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Expand Up @@ -394,6 +394,18 @@ static zend_long php_session_gc(bool immediate) /* {{{ */
/* GC must be done before reading session data. */
if ((PS(mod_data) || PS(mod_user_implemented))) {
if (!collect && PS(gc_probability) > 0) {
/* Seed lazily on first GC draw per process. */
if (UNEXPECTED(!PS(random_seeded))) {
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(random).state, seed);
PS(random_seeded) = true;
}
collect = php_random_range(PS(random), 0, PS(gc_divisor) - 1) < PS(gc_probability);
}

Expand Down Expand Up @@ -2984,14 +2996,7 @@ static PHP_GINIT_FUNCTION(ps) /* {{{ */
.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);
ps_globals->random_seeded = false;
}
/* }}} */

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