s390/qeth: fix locking for discipline setup / removal

Due to insufficient locking, qeth_core_set_online() and
qeth_dev_layer2_store() can run in parallel, both attempting to load &
setup the discipline (and stepping on each other toes along the way).
A similar race can also occur between qeth_core_remove_device() and
qeth_dev_layer2_store().

Access to .discipline is meant to be protected by the discipline_mutex,
so add/expand the locking in qeth_core_remove_device() and
qeth_core_set_online().
Adjust the locking in qeth_l*_remove_device() accordingly, as it's now
handled by the callers in a consistent manner.

Based on an initial patch by Ursula Braun.

Fixes: 9dc48ccc68b9 ("qeth: serialize sysfs-triggered device configurations")
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Reviewed-by: Alexandra Winter <wintera@linux.ibm.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/s390/net/qeth_core_main.c b/drivers/s390/net/qeth_core_main.c
index d45e223..cf18d87 100644 (file)
--- a/drivers/s390/net/qeth_core_main.c
+++ b/drivers/s390/net/qeth_core_main.c
@@ -6585,6 +6585,7 @@ static int qeth_core_probe_device(struct ccwgroup_device *gdev)
                break;
        default:
                card->info.layer_enforced = true;
+               /* It's so early that we don't need the discipline_mutex yet. */
                rc = qeth_core_load_discipline(card, enforced_disc);
                if (rc)
                        goto err_load;
@@ -6617,10 +6618,12 @@ static void qeth_core_remove_device(struct ccwgroup_device *gdev)
 
        QETH_CARD_TEXT(card, 2, "removedv");
 
+       mutex_lock(&card->discipline_mutex);
        if (card->discipline) {
                card->discipline->remove(gdev);
                qeth_core_free_discipline(card);
        }
+       mutex_unlock(&card->discipline_mutex);
 
        qeth_free_qdio_queues(card);
 
@@ -6635,6 +6638,7 @@ static int qeth_core_set_online(struct ccwgroup_device *gdev)
        int rc = 0;
        enum qeth_discipline_id def_discipline;
 
+       mutex_lock(&card->discipline_mutex);
        if (!card->discipline) {
                def_discipline = IS_IQD(card) ? QETH_DISCIPLINE_LAYER3 :
                                                QETH_DISCIPLINE_LAYER2;
@@ -6648,11 +6652,10 @@ static int qeth_core_set_online(struct ccwgroup_device *gdev)
                }
        }
 
-       mutex_lock(&card->discipline_mutex);
        rc = qeth_set_online(card, card->discipline);
-       mutex_unlock(&card->discipline_mutex);
 
 err:
+       mutex_unlock(&card->discipline_mutex);
        return rc;
 }
 

diff --git a/drivers/s390/net/qeth_l2_main.c b/drivers/s390/net/qeth_l2_main.c
index 37279b1..4254caf 100644 (file)
--- a/drivers/s390/net/qeth_l2_main.c
+++ b/drivers/s390/net/qeth_l2_main.c
@@ -2207,11 +2207,8 @@ static void qeth_l2_remove_device(struct ccwgroup_device *gdev)
        qeth_set_allowed_threads(card, 0, 1);
        wait_event(card->wait_q, qeth_threads_running(card, 0xffffffff) == 0);
 
-       if (gdev->state == CCWGROUP_ONLINE) {
-               mutex_lock(&card->discipline_mutex);
+       if (gdev->state == CCWGROUP_ONLINE)
                qeth_set_offline(card, card->discipline, false);
-               mutex_unlock(&card->discipline_mutex);
-       }
 
        cancel_work_sync(&card->close_dev_work);
        if (card->dev->reg_state == NETREG_REGISTERED)

diff --git a/drivers/s390/net/qeth_l3_main.c b/drivers/s390/net/qeth_l3_main.c
index 8d47417..6970597 100644 (file)
--- a/drivers/s390/net/qeth_l3_main.c
+++ b/drivers/s390/net/qeth_l3_main.c
@@ -1970,11 +1970,8 @@ static void qeth_l3_remove_device(struct ccwgroup_device *cgdev)
        qeth_set_allowed_threads(card, 0, 1);
        wait_event(card->wait_q, qeth_threads_running(card, 0xffffffff) == 0);
 
-       if (cgdev->state == CCWGROUP_ONLINE) {
-               mutex_lock(&card->discipline_mutex);
+       if (cgdev->state == CCWGROUP_ONLINE)
                qeth_set_offline(card, card->discipline, false);
-               mutex_unlock(&card->discipline_mutex);
-       }
 
        cancel_work_sync(&card->close_dev_work);
        if (card->dev->reg_state == NETREG_REGISTERED)