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From: Olivier Matz <olivier.matz@6wind.com>
To: Luc Pelletier <lucp.at.work@gmail.com>
Cc: jianfeng.tan@intel.com, Honnappa.Nagarahalli@arm.com,
	dev@dpdk.org, stable@dpdk.org
Subject: Re: [dpdk-stable] [PATCH v5] eal: fix race in ctrl thread creation
Date: Wed, 7 Apr 2021 15:31:05 +0200
Message-ID: <20210407133105.GL1650@platinum> (raw)
In-Reply-To: <20210407125322.124327-1-lucp.at.work@gmail.com>

Hi Luc,

On Wed, Apr 07, 2021 at 08:53:23AM -0400, Luc Pelletier wrote:
> 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")
> Cc: jianfeng.tan@intel.com
> Cc: stable@dpdk.org
> 
> Signed-off-by: Luc Pelletier <lucp.at.work@gmail.com>
> ---
> 
> Same as v4 except that I fixed 2 minor style issues flagged by patchwork.
> 
>  lib/librte_eal/common/eal_common_thread.c | 52 +++++++++++------------
>  1 file changed, 25 insertions(+), 27 deletions(-)
> 
> diff --git a/lib/librte_eal/common/eal_common_thread.c b/lib/librte_eal/common/eal_common_thread.c
> index 73a055902..c1044e795 100644
> --- a/lib/librte_eal/common/eal_common_thread.c
> +++ b/lib/librte_eal/common/eal_common_thread.c
> @@ -170,11 +170,19 @@ 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) {
> +		pthread_barrier_destroy(&params->configured);
> +		free(params);
> +	}
> +}
> +
>  static void *ctrl_thread_init(void *arg)
>  {
> -	int ret;
>  	struct internal_config *internal_conf =
>  		eal_get_internal_configuration();
>  	rte_cpuset_t *cpuset = &internal_conf->ctrl_cpuset;
> @@ -184,11 +192,8 @@ static void *ctrl_thread_init(void *arg)
>  
>  	__rte_thread_init(rte_lcore_id(), cpuset);
>  
> -	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);
>  }
> @@ -210,14 +215,15 @@ 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_barrier_init(&params->configured, NULL, 2);
> +	if (ret != 0)
> +		goto fail_no_barrier;
>  
>  	ret = pthread_create(thread, attr, ctrl_thread_init, (void *)params);
> -	if (ret != 0) {
> -		free(params);
> -		return -ret;
> -	}
> +	if (ret != 0)
> +		goto fail_with_barrier;
>  
>  	if (name != NULL) {
>  		ret = rte_thread_setname(*thread, name);
> @@ -227,25 +233,17 @@ rte_ctrl_thread_create(pthread_t *thread, const char *name,
>  	}
>  
>  	ret = pthread_setaffinity_np(*thread, sizeof(*cpuset), cpuset);
> -	if (ret)
> -		goto fail;
> +	pthread_barrier_wait(&params->configured);
> +	ctrl_params_free(params);
>  
> -	ret = pthread_barrier_wait(&params->configured);
> -	if (ret == PTHREAD_BARRIER_SERIAL_THREAD) {
> -		pthread_barrier_destroy(&params->configured);
> -		free(params);
> -	}
> +	return -ret;

I think not killing the thread when pthread_setaffinity_np() returns an
error is not very understandable from the API user point of view.

What about doing this on top of your patch? The idea is to set
start_routine to NULL before the barrier if pthread_setaffinity_np()
failed. So there is no need to cancel the thread, it will exit by
itself.

  @@ -187,14 +187,18 @@ static void *ctrl_thread_init(void *arg)
                  eal_get_internal_configuration();
          rte_cpuset_t *cpuset = &internal_conf->ctrl_cpuset;
          struct rte_thread_ctrl_params *params = arg;
  -       void *(*start_routine)(void *) = params->start_routine;
  +       void *(*start_routine)(void *);
          void *routine_arg = params->arg;
   
          __rte_thread_init(rte_lcore_id(), cpuset);
   
          pthread_barrier_wait(&params->configured);
  +       start_routine = params->start_routine;
          ctrl_params_free(params);
   
  +       if (start_routine == NULL)
  +               return NULL;
  +
          return start_routine(routine_arg);
   }
   
  @@ -233,10 +237,18 @@ rte_ctrl_thread_create(pthread_t *thread, const char *name,
          }
   
          ret = pthread_setaffinity_np(*thread, sizeof(*cpuset), cpuset);
  +       if (ret != 0)
  +               params->start_routine = NULL;
  +
          pthread_barrier_wait(&params->configured);
          ctrl_params_free(params);
   
  -       return -ret;
  +       if (ret != 0) {
  +               pthread_join(*thread, NULL);
  +               return -ret;
  +       }
  +
  +       return 0;
   
   fail_with_barrier:
          pthread_barrier_destroy(&params->configured);


Regards,
Olivier

  parent reply	other threads:[~2021-04-07 13:31 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-24 13:04 [dpdk-stable] [PATCH] eal: fix possible UB on creation of ctrl thread Luc Pelletier
2021-03-25 11:27 ` [dpdk-stable] [PATCH v2] eal: fix race in ctrl thread creation Olivier Matz
2021-03-25 14:42   ` Luc Pelletier
2021-04-02  4:34   ` [dpdk-stable] [dpdk-dev] " Honnappa Nagarahalli
2021-04-06 16:15 ` [dpdk-stable] [PATCH v3] " Luc Pelletier
2021-04-06 21:10   ` Honnappa Nagarahalli
2021-04-07 12:35     ` [dpdk-stable] [PATCH v4] " Luc Pelletier
2021-04-07 12:53       ` [dpdk-stable] [PATCH v5] " Luc Pelletier
2021-04-07 13:22         ` Luc Pelletier
2021-04-07 13:31         ` Olivier Matz [this message]
2021-04-07 14:42           ` [dpdk-stable] [PATCH v6] " Luc Pelletier
2021-04-07 14:57             ` Olivier Matz
2021-04-07 15:29               ` [dpdk-stable] [PATCH v7] " Luc Pelletier
2021-04-07 17:15                 ` Honnappa Nagarahalli
2021-04-07 15:15           ` [dpdk-stable] [PATCH v5] " Honnappa Nagarahalli
2021-04-07 20:16             ` [dpdk-stable] [PATCH 1/2] " Luc Pelletier
2021-04-08 14:17               ` Olivier Matz
2021-04-08 17:06               ` Honnappa Nagarahalli
2021-04-07 20:16             ` [dpdk-stable] [PATCH 2/2] eal: fix hang in ctrl thread creation error logic Luc Pelletier
2021-04-08 14:20               ` Olivier Matz
2021-04-08 18:01                 ` Luc Pelletier
2021-04-09  8:13                   ` [dpdk-stable] [dpdk-dev] " David Marchand
2021-04-08 17:07               ` [dpdk-stable] " Honnappa Nagarahalli
2021-04-09 14:34               ` David Marchand

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