[php-src] PHP-8.4: ext/session: fix GH-21314 (session GC behaviour is different since 8.4)

Author: Jorg Sowa (jorgsowa)
Committer: Gina Peter Banyard (Girgias)
Date: 2026-07-02T11:49:56+01:00

Commit: https://github.com/php/php-src/commit/fe53521e92eb141a3365df8e98eb41003cdf0887
Raw diff: https://github.com/php/php-src/commit/fe53521e92eb141a3365df8e98eb41003cdf0887.diff

ext/session: fix GH-21314 (session GC behaviour is different since 8.4)

Closes GH-22164

Changed paths:
  M  ext/session/php_session.h
  M  ext/session/session.c


Diff:

diff --git a/ext/session/php_session.h b/ext/session/php_session.h
index dfa7632e5a44..b52cf43dfba3 100644
--- a/ext/session/php_session.h
+++ b/ext/session/php_session.h
@@ -202,6 +202,7 @@ typedef struct _php_ps_globals {
 	bool lazy_write; /* omit session write when it is possible */
 	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 */
+	bool random_seeded;
 	zend_string *session_vars; /* serialized original session data */
 } php_ps_globals;
 
diff --git a/ext/session/session.c b/ext/session/session.c
index 70e1673d87f5..ba71d709a536 100644
--- a/ext/session/session.c
+++ b/ext/session/session.c
@@ -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);
 		}
 
@@ -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;
 }
 /* }}} */