netdev - [PATCH net] s390/qeth: fix use-after-free in hsci

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Date:   Tue,  6 Dec 2022 15:56:14 +0100
From:   Alexandra Winter <wintera@...ux.ibm.com>
To:     David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, linux-s390@...r.kernel.org,
        Heiko Carstens <hca@...ux.ibm.com>,
        Alexandra Winter <wintera@...ux.ibm.com>,
        Thorsten Winkler <twinkler@...ux.ibm.com>,
        Wenjia Zhang <wenjia@...ux.ibm.com>
Subject: [PATCH net] s390/qeth: fix use-after-free in hsci

KASAN found that addr was dereferenced after br2dev_event_work was freed.

Fixes: f7936b7b2663 ("s390/qeth: Update MACs of LEARNING_SYNC device")
Reported-by: Thorsten Winkler <twinkler@...ux.ibm.com>
Signed-off-by: Alexandra Winter <wintera@...ux.ibm.com>
Reviewed-by: Wenjia Zhang <wenjia@...ux.ibm.com>
Reviewed-by: Thorsten Winkler <twinkler@...ux.ibm.com>
---
 drivers/s390/net/qeth_l2_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/s390/net/qeth_l2_main.c b/drivers/s390/net/qeth_l2_main.c
index 9dc935886e9f..c6ded3fdd715 100644
--- a/drivers/s390/net/qeth_l2_main.c
+++ b/drivers/s390/net/qeth_l2_main.c
@@ -758,7 +758,6 @@ static void qeth_l2_br2dev_worker(struct work_struct *work)
 	struct list_head *iter;
 	int err = 0;
 
-	kfree(br2dev_event_work);
 	QETH_CARD_TEXT_(card, 4, "b2dw%04lx", event);
 	QETH_CARD_TEXT_(card, 4, "ma%012llx", ether_addr_to_u64(addr));
 
@@ -815,6 +814,7 @@ static void qeth_l2_br2dev_worker(struct work_struct *work)
 	dev_put(brdev);
 	dev_put(lsyncdev);
 	dev_put(dstdev);
+	kfree(br2dev_event_work);
 }
 
 static int qeth_l2_br2dev_queue_work(struct net_device *brdev,
-- 
2.34.1