From: Neil Horman Date: Fri, 10 Jan 2025 19:37:28 +0000 (-0500) Subject: Fix premature reuse of qp's in rcu locks X-Git-Tag: openssl-3.5.0-alpha1~750 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=25f8e2c15b701514b7b2fe652634289b6fb8581f;p=thirdparty%2Fopenssl.git Fix premature reuse of qp's in rcu locks An intermittent failure was noted on our new ppc64le CI runner, in which what appeared to be a corrupted or invalid value getting returned from a shared pointer under rcu protection Investigation showed that the problem was with our small number of qp's in a lock, and slightly incorrect accounting of the number of qp's available we were prematurely recycling qp's, which led in turn to premature completion of synchronization states, resulting in readers reading memory that may have already been freed. Fix it by: a) Ensuring that we account for the fact that the first qp in an rcu lock is allocated at the time the lock is created and b) Ensuring that we have a minimum number of 3 qp's: 1 that is free for write side allocation 1 that is in use by the write side currently 1 "next" qp that the read side can update while the prior qp is being retired With this change, the rcu threadstest runs indefinately in my testing Fixes #26356 Reviewed-by: Paul Dale Reviewed-by: Tomas Mraz Reviewed-by: Saša Nedvědický Reviewed-by: Matt Caswell (Merged from https://github.com/openssl/openssl/pull/26384) --- diff --git a/crypto/threads_pthread.c b/crypto/threads_pthread.c index bfd04fa4f15..4e8df06207b 100644 --- a/crypto/threads_pthread.c +++ b/crypto/threads_pthread.c @@ -667,8 +667,11 @@ CRYPTO_RCU_LOCK *ossl_rcu_lock_new(int num_writers, OSSL_LIB_CTX *ctx) { struct rcu_lock_st *new; - if (num_writers < 1) - num_writers = 1; + /* + * We need a minimum of 3 qp's + */ + if (num_writers < 3) + num_writers = 3; ctx = ossl_lib_ctx_get_concrete(ctx); if (ctx == NULL) @@ -684,11 +687,15 @@ CRYPTO_RCU_LOCK *ossl_rcu_lock_new(int num_writers, OSSL_LIB_CTX *ctx) pthread_mutex_init(&new->alloc_lock, NULL); pthread_cond_init(&new->prior_signal, NULL); pthread_cond_init(&new->alloc_signal, NULL); - new->qp_group = allocate_new_qp_group(new, num_writers + 1); + /* By default our first writer is already alloced */ + new->writers_alloced = 1; + + new->qp_group = allocate_new_qp_group(new, num_writers); if (new->qp_group == NULL) { OPENSSL_free(new); new = NULL; } + return new; } diff --git a/crypto/threads_win.c b/crypto/threads_win.c index bdbd4d381f0..03a22fd2c92 100644 --- a/crypto/threads_win.c +++ b/crypto/threads_win.c @@ -159,8 +159,11 @@ CRYPTO_RCU_LOCK *ossl_rcu_lock_new(int num_writers, OSSL_LIB_CTX *ctx) { struct rcu_lock_st *new; - if (num_writers < 1) - num_writers = 1; + /* + * We need a minimum of 3 qps + */ + if (num_writers < 3) + num_writers = 3; ctx = ossl_lib_ctx_get_concrete(ctx); if (ctx == NULL) @@ -178,7 +181,9 @@ CRYPTO_RCU_LOCK *ossl_rcu_lock_new(int num_writers, OSSL_LIB_CTX *ctx) new->prior_signal = ossl_crypto_condvar_new(); new->alloc_lock = ossl_crypto_mutex_new(); new->prior_lock = ossl_crypto_mutex_new(); - new->qp_group = allocate_new_qp_group(new, num_writers + 1); + new->qp_group = allocate_new_qp_group(new, num_writers); + /* By default the first qp is already alloced */ + new->writers_alloced = 1; if (new->qp_group == NULL || new->alloc_signal == NULL || new->prior_signal == NULL @@ -196,6 +201,7 @@ CRYPTO_RCU_LOCK *ossl_rcu_lock_new(int num_writers, OSSL_LIB_CTX *ctx) OPENSSL_free(new); new = NULL; } + return new; }