[dpdk-stable] [PATCH v3] eal: fix race in ctrl thread creation
Luc Pelletier
lucp.at.work at gmail.com
Tue Apr 6 18:15:35 CEST 2021
The creation of control threads used 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. The barrier has been completely removed in favour
of a reference count on the control thread parameters struct.
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,
Hi Honnappa,
Thanks for your input Honnappa. I've made the changes to completely
remove the barrier. However, I didn't move the call to
pthread_setaffinity_np to the control thread; I think we want to report
the result of that function to the caller of rte_ctrl_thread_create and
doing so from ctrl_thread_init would be a lot trickier.
Olivier, what do you think of these changes?
lib/librte_eal/common/eal_common_thread.c | 35 ++++++++---------------
1 file changed, 12 insertions(+), 23 deletions(-)
diff --git a/lib/librte_eal/common/eal_common_thread.c b/lib/librte_eal/common/eal_common_thread.c
index 73a055902..2421066f9 100644
--- a/lib/librte_eal/common/eal_common_thread.c
+++ b/lib/librte_eal/common/eal_common_thread.c
@@ -169,12 +169,11 @@ __rte_thread_uninit(void)
struct rte_thread_ctrl_params {
void *(*start_routine)(void *);
void *arg;
- pthread_barrier_t configured;
+ unsigned int refcnt;
};
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 +183,8 @@ static void *ctrl_thread_init(void *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);
+ if (__atomic_sub_fetch(¶ms->refcnt, 1, __ATOMIC_ACQ_REL) == 0)
free(params);
- }
return start_routine(routine_arg);
}
@@ -210,14 +206,11 @@ rte_ctrl_thread_create(pthread_t *thread, const char *name,
params->start_routine = start_routine;
params->arg = arg;
-
- pthread_barrier_init(¶ms->configured, NULL, 2);
+ params->refcnt = 2;
ret = pthread_create(thread, attr, ctrl_thread_init, (void *)params);
- if (ret != 0) {
- free(params);
- return -ret;
- }
+ if (ret != 0)
+ goto fail;
if (name != NULL) {
ret = rte_thread_setname(*thread, name);
@@ -228,24 +221,20 @@ rte_ctrl_thread_create(pthread_t *thread, const char *name,
ret = pthread_setaffinity_np(*thread, sizeof(*cpuset), cpuset);
if (ret)
- goto fail;
+ goto fail_cancel;
- ret = pthread_barrier_wait(¶ms->configured);
- if (ret == PTHREAD_BARRIER_SERIAL_THREAD) {
- pthread_barrier_destroy(¶ms->configured);
+ if (__atomic_sub_fetch(¶ms->refcnt, 1, __ATOMIC_ACQ_REL) == 0)
free(params);
- }
return 0;
-fail:
- if (PTHREAD_BARRIER_SERIAL_THREAD ==
- pthread_barrier_wait(¶ms->configured)) {
- pthread_barrier_destroy(¶ms->configured);
- free(params);
- }
+fail_cancel:
pthread_cancel(*thread);
pthread_join(*thread, NULL);
+
+fail:
+ free(params);
+
return -ret;
}
--
2.25.1
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