[dpdk-stable] [PATCH 19.11.9 1/2] eal: fix race in control thread creation

[Christian Ehrhardt]

On Fri, May 21, 2021 at 5:49 PM Luc Pelletier <lucp.at.work at gmail.com> wrote:
>
> [ upstream commit 34cc55cce6b180a6c3ee3fcf70a0fd56927f240d ]
>
> The creation of control threads uses a pthread barrier for
> synchronization. This patch fixes a race condition where the pthread
> barrier could get destroyed while one of the threads has not yet
> returned from the pthread_barrier_wait function, which could result in
> undefined behaviour.
>
> Fixes: 3a0d465d4c53 ("eal: fix use-after-free on control thread creation")
> ---

Thank you, applied to 19.11.9 (to become -rc2) now

>  lib/librte_eal/common/eal_common_thread.c | 49 +++++++++++++----------
>  1 file changed, 27 insertions(+), 22 deletions(-)
>
> diff --git a/lib/librte_eal/common/eal_common_thread.c b/lib/librte_eal/common/eal_common_thread.c
> index f9a8cf14d..a5089ae49 100644
> --- a/lib/librte_eal/common/eal_common_thread.c
> +++ b/lib/librte_eal/common/eal_common_thread.c
> @@ -147,20 +147,25 @@ struct rte_thread_ctrl_params {
>         void *(*start_routine)(void *);
>         void *arg;
>         pthread_barrier_t configured;
> +       unsigned int refcnt;
>  };
>
> +static void ctrl_params_free(struct rte_thread_ctrl_params *params)
> +{
> +       if (__atomic_sub_fetch(&params->refcnt, 1, __ATOMIC_ACQ_REL) == 0) {
> +               (void)pthread_barrier_destroy(&params->configured);
> +               free(params);
> +       }
> +}
> +
>  static void *rte_thread_init(void *arg)
>  {
> -       int ret;
>         struct rte_thread_ctrl_params *params = arg;
>         void *(*start_routine)(void *) = params->start_routine;
>         void *routine_arg = params->arg;
>
> -       ret = pthread_barrier_wait(&params->configured);
> -       if (ret == PTHREAD_BARRIER_SERIAL_THREAD) {
> -               pthread_barrier_destroy(&params->configured);
> -               free(params);
> -       }
> +       pthread_barrier_wait(&params->configured);
> +       ctrl_params_free(params);
>
>         return start_routine(routine_arg);
>  }
> @@ -180,15 +185,18 @@ rte_ctrl_thread_create(pthread_t *thread, const char *name,
>
>         params->start_routine = start_routine;
>         params->arg = arg;
> +       params->refcnt = 2;
>
> -       pthread_barrier_init(&params->configured, NULL, 2);
> -
> -       ret = pthread_create(thread, attr, rte_thread_init, (void *)params);
> +       ret = pthread_barrier_init(&params->configured, NULL, 2);
>         if (ret != 0) {
>                 free(params);
>                 return -ret;
>         }
>
> +       ret = pthread_create(thread, attr, rte_thread_init, (void *)params);
> +       if (ret != 0)
> +               goto fail;
> +
>         if (name != NULL) {
>                 ret = rte_thread_setname(*thread, name);
>                 if (ret < 0)
> @@ -197,24 +205,21 @@ rte_ctrl_thread_create(pthread_t *thread, const char *name,
>         }
>
>         ret = pthread_setaffinity_np(*thread, sizeof(*cpuset), cpuset);
> -       if (ret)
> -               goto fail;
> +       if (ret != 0)
> +               goto fail_cancel;
>
> -       ret = pthread_barrier_wait(&params->configured);
> -       if (ret == PTHREAD_BARRIER_SERIAL_THREAD) {
> -               pthread_barrier_destroy(&params->configured);
> -               free(params);
> -       }
> +       pthread_barrier_wait(&params->configured);
> +       ctrl_params_free(params);
>
>         return 0;
>
> -fail:
> -       if (PTHREAD_BARRIER_SERIAL_THREAD ==
> -           pthread_barrier_wait(&params->configured)) {
> -               pthread_barrier_destroy(&params->configured);
> -               free(params);
> -       }
> +fail_cancel:
>         pthread_cancel(*thread);
>         pthread_join(*thread, NULL);
> +
> +fail:
> +       (void)pthread_barrier_destroy(&params->configured);
> +       free(params);
> +
>         return -ret;
>  }
> --
> 2.25.1
>


-- 
Christian Ehrhardt
Staff Engineer, Ubuntu Server
Canonical Ltd