linux-kernel - [PATCH 3.16 097/202] s390/qeth: cancel close

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Message-ID: <lsq.1556377989.618660317@decadent.org.uk>
Date:   Sat, 27 Apr 2019 16:13:09 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Julian Wiedmann" <jwi@...ux.ibm.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 3.16 097/202] s390/qeth: cancel close_dev work before
 removing a card

3.16.66-rc1 review patch.  If anyone has any objections, please let me know.

------------------

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

commit c2780c1a3fb724560b1d44f7976e0de17bf153c7 upstream.

A card's close_dev work is scheduled on a driver-wide workqueue. If the
card is removed and freed while the work is still active, this causes a
use-after-free.
So make sure that the work is completed before freeing the card.

Fixes: 0f54761d167f ("qeth: Support VEPA mode")
Signed-off-by: Julian Wiedmann <jwi@...ux.ibm.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/s390/net/qeth_core.h    | 1 +
 drivers/s390/net/qeth_l2_main.c | 2 ++
 drivers/s390/net/qeth_l3_main.c | 1 +
 3 files changed, 4 insertions(+)

--- a/drivers/s390/net/qeth_core.h
+++ b/drivers/s390/net/qeth_core.h
@@ -18,6 +18,7 @@
 #include <linux/bitops.h>
 #include <linux/seq_file.h>
 #include <linux/ethtool.h>
+#include <linux/workqueue.h>
 
 #include <net/ipv6.h>
 #include <net/if_inet6.h>
--- a/drivers/s390/net/qeth_l2_main.c
+++ b/drivers/s390/net/qeth_l2_main.c
@@ -924,6 +924,7 @@ static void qeth_l2_remove_device(struct
 	if (cgdev->state == CCWGROUP_ONLINE)
 		qeth_l2_set_offline(cgdev);
 
+	cancel_work_sync(&card->close_dev_work);
 	if (card->dev) {
 		unregister_netdev(card->dev);
 		free_netdev(card->dev);
--- a/drivers/s390/net/qeth_l3_main.c
+++ b/drivers/s390/net/qeth_l3_main.c
@@ -3342,6 +3342,7 @@ static void qeth_l3_remove_device(struct
 	if (cgdev->state == CCWGROUP_ONLINE)
 		qeth_l3_set_offline(cgdev);
 
+	cancel_work_sync(&card->close_dev_work);
 	if (card->dev) {
 		unregister_netdev(card->dev);
 		free_netdev(card->dev);