int SSL_set_session(SSL *s, SSL_SESSION *session)
{
    int ret = 0;
    const SSL_METHOD *meth;

    if (session != NULL) {
        meth = s->ctx->method->get_ssl_method(session->ssl_version);
        if (meth == NULL)
            meth = s->method->get_ssl_method(session->ssl_version);
        if (meth == NULL) {
            SSLerr(SSL_F_SSL_SET_SESSION, SSL_R_UNABLE_TO_FIND_SSL_METHOD);
            return (0);
        }

        if (meth != s->method) {
            if (!SSL_set_ssl_method(s, meth))
                return (0);
        }

        /* CRYPTO_w_lock(CRYPTO_LOCK_SSL); */
        CRYPTO_add(&session->references, 1, CRYPTO_LOCK_SSL_SESSION);
        SSL_SESSION_free(s->session);
        s->session = session;
        s->verify_result = s->session->verify_result;
        /* CRYPTO_w_unlock(CRYPTO_LOCK_SSL); */
        ret = 1;
    } else {
        SSL_SESSION_free(s->session);
        s->session = NULL;
        meth = s->ctx->method;
        if (meth != s->method) {
            if (!SSL_set_ssl_method(s, meth))
                return (0);
        }
        ret = 1;
    }
    return (ret);
}

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.