[dpdk-dev] [PATCH v7] eal: fix race in ctrl thread creation
Luc Pelletier
lucp.at.work at gmail.com
Wed Apr 7 17:29:04 CEST 2021
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 at intel.com
Cc: stable at dpdk.org
Signed-off-by: Luc Pelletier <lucp.at.work at gmail.com>
---
Hi Olivier,
Olivier, thanks for pointing out that pthread_barrier_wait acts as a
full memory barrier; I didn't know that was explicitly specified in the
documentation. I've changed it to use a regular read/write.
Hi Honnappa,
I have not changed the code to use pthread_attr_setaffinity_np because
the attr parameter is const. I could make a copy of the provided
attributes and use that instead, but I think this would still violate
the spirit of the API and, AFAICT, there's no official mechanism for
copying a pthread_attr_t.
Please let me know what you think.
lib/librte_eal/common/eal_common_thread.c | 63 +++++++++++++----------
1 file changed, 35 insertions(+), 28 deletions(-)
diff --git a/lib/librte_eal/common/eal_common_thread.c b/lib/librte_eal/common/eal_common_thread.c
index 73a055902..d4e09f84b 100644
--- a/lib/librte_eal/common/eal_common_thread.c
+++ b/lib/librte_eal/common/eal_common_thread.c
@@ -170,25 +170,34 @@ 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(¶ms->refcnt, 1, __ATOMIC_ACQ_REL) == 0) {
+ pthread_barrier_destroy(¶ms->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;
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);
- ret = pthread_barrier_wait(¶ms->configured);
- if (ret == PTHREAD_BARRIER_SERIAL_THREAD) {
- pthread_barrier_destroy(¶ms->configured);
- free(params);
- }
+ pthread_barrier_wait(¶ms->configured);
+ start_routine = params->start_routine;
+ ctrl_params_free(params);
+
+ if (start_routine == NULL)
+ return NULL;
return start_routine(routine_arg);
}
@@ -210,14 +219,15 @@ rte_ctrl_thread_create(pthread_t *thread, const char *name,
params->start_routine = start_routine;
params->arg = arg;
+ params->refcnt = 2;
- pthread_barrier_init(¶ms->configured, NULL, 2);
+ ret = pthread_barrier_init(¶ms->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 +237,22 @@ 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)
+ params->start_routine = NULL;
+ pthread_barrier_wait(¶ms->configured);
+ ctrl_params_free(params);
- ret = pthread_barrier_wait(¶ms->configured);
- if (ret == PTHREAD_BARRIER_SERIAL_THREAD) {
- pthread_barrier_destroy(¶ms->configured);
- free(params);
- }
+ if (ret != 0)
+ pthread_join(*thread, NULL);
- return 0;
+ return -ret;
+
+fail_with_barrier:
+ pthread_barrier_destroy(¶ms->configured);
+
+fail_no_barrier:
+ free(params);
-fail:
- if (PTHREAD_BARRIER_SERIAL_THREAD ==
- pthread_barrier_wait(¶ms->configured)) {
- pthread_barrier_destroy(¶ms->configured);
- free(params);
- }
- pthread_cancel(*thread);
- pthread_join(*thread, NULL);
return -ret;
}
--
2.25.1
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