Re: [dpdk-dev] [PATCH v2] eal: fix use-after-free issue on thread creation

["Tan, Jianfeng" <jianfeng.tan@intel.com>]

Hi Olivier,


On 5/2/2018 7:24 PM, Olivier Matz wrote:
> Hi Jianfeng,
>
> On Wed, May 02, 2018 at 10:17:50AM +0000, Jianfeng Tan wrote:
>> After below commit, we encounter some strange issue:
>>    1) Dead lock as described here:
>>       http://dpdk.org/ml/archives/dev/2018-April/099806.html
>>    2) SIGSEGV issue when starting a testpmd in VM.
>>
>> Considering below commit changes to use dynamic memory instead of
>> stack for memory barrier, we doubt it's caused by use-after-free.
>>
>> Fixes: 3d09a6e26d8b ("eal: fix threads block on barrier")
>>
>> Reported-by: Maxime Coquelin <maxime.coquelin@redhat.com>
>> Reported-by: Lei Yao <lei.a.yao@intel.com>
>> Suggested-by: Stephen Hemminger <stephen@networkplumber.org>
>> Signed-off-by: Jianfeng Tan <jianfeng.tan@intel.com>
>> ---
>>   v1->v2:
>>   - Destroy barrier if failure happens.
>>   lib/librte_eal/common/eal_common_thread.c | 15 ++++++++++++---
>>   1 file changed, 12 insertions(+), 3 deletions(-)
>>
>> diff --git a/lib/librte_eal/common/eal_common_thread.c b/lib/librte_eal/common/eal_common_thread.c
>> index de69452..5f0c61f 100644
>> --- a/lib/librte_eal/common/eal_common_thread.c
>> +++ b/lib/librte_eal/common/eal_common_thread.c
>> @@ -149,11 +149,16 @@ struct rte_thread_ctrl_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;
>>   
>> -	pthread_barrier_wait(&params->configured);
>> +	ret = pthread_barrier_wait(&params->configured);
>> +	if (ret == PTHREAD_BARRIER_SERIAL_THREAD) {
>> +		pthread_barrier_destroy(&params->configured);
>> +		free(params);
>> +	}
>>   
>>   	return start_routine(routine_arg);
>>   }
>> @@ -204,12 +209,16 @@ rte_ctrl_thread_create(pthread_t *thread, const char *name,
>>   	if (ret < 0)
>>   		goto fail;
>>   
>> -	pthread_barrier_wait(&params->configured);
>> -	free(params);
>> +	ret = pthread_barrier_wait(&params->configured);
>> +	if (ret == PTHREAD_BARRIER_SERIAL_THREAD) {
>> +		pthread_barrier_destroy(&params->configured);
>> +		free(params);
>> +	}
>>   
>>   	return 0;
>>   
>>   fail:
>> +	pthread_barrier_destroy(&params->configured);
> I think we should have the same code than above in the fail case:
>
> 	ret = pthread_barrier_wait(&params->configured);
> 	if (ret == PTHREAD_BARRIER_SERIAL_THREAD) {
> 		pthread_barrier_destroy(&params->configured);
> 		free(params);
> 	}
>
> Else, the child will wait forever on the barrier on failure.

Make sense. I send v3 patch according to your advice, except that not 
polluting ret.

Thanks,
Jianfeng

>
> This can be tested with this standalone program:
> https://www.droids-corp.org/~zer0/hidden/ctrl_thread.c
>
> gcc -W -Wall -Werror -Wextra -pthread ctrl_thread.c
> ./a.out -> fail
>
> gcc -W -Wall -Werror -Wextra -pthread -DFIX ctrl_thread.c
> ./a.out -> ok
>
>
>
>>   	pthread_cancel(*thread);
>>   	pthread_join(*thread, NULL);
>>   	free(params);
>> -- 
>> 2.7.4
>>