[PATCH 5.10 041/103] s390/qeth: fix locking for discipline setup / removal

Greg Kroah-Hartman
2021-01-15T12:46:43Z

From: Julian Wiedmann <jwi@linux.ibm.com>

[ Upstream commit b41b554c1ee75070a14c02a88496b1f231c7eacc ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/s390/net/qeth_core_main.c | 7 +++++--
drivers/s390/net/qeth_l2_main.c | 5 +----
drivers/s390/net/qeth_l3_main.c | 5 +----
3 files changed, 7 insertions(+), 10 deletions(-)

--- a/drivers/s390/net/qeth_core_main.c
+++ b/drivers/s390/net/qeth_core_main.c
@@ -6361,6 +6361,7 @@ static int qeth_core_probe_device(struct
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;
@@ -6393,10 +6394,12 @@ static void qeth_core_remove_device(stru

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);

@@ -6411,6 +6414,7 @@ static int qeth_core_set_online(struct c
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;
@@ -6424,11 +6428,10 @@ static int qeth_core_set_online(struct c
}
}

- 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;
}

--- 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
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)
--- a/drivers/s390/net/qeth_l3_main.c
+++ b/drivers/s390/net/qeth_l3_main.c
@@ -1973,11 +1973,8 @@ static void qeth_l3_remove_device(struct
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)