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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Yu Zhao <yuzhao@google.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.4 25/48] net/usb: cancel pending work when unbinding smsc75xx
Date:   Thu, 18 Oct 2018 19:55:00 +0200
Message-Id: <20181018175429.333929086@linuxfoundation.org>
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4.4-stable review patch.  If anyone has any objections, please let me know.

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

From: Yu Zhao <yuzhao@google.com>

[ Upstream commit f7b2a56e1f3dcbdb4cf09b2b63e859ffe0e09df8 ]

Cancel pending work before freeing smsc75xx private data structure
during binding. This fixes the following crash in the driver:

BUG: unable to handle kernel NULL pointer dereference at 0000000000000050
IP: mutex_lock+0x2b/0x3f
<snipped>
Workqueue: events smsc75xx_deferred_multicast_write [smsc75xx]
task: ffff8caa83e85700 task.stack: ffff948b80518000
RIP: 0010:mutex_lock+0x2b/0x3f
<snipped>
Call Trace:
 smsc75xx_deferred_multicast_write+0x40/0x1af [smsc75xx]
 process_one_work+0x18d/0x2fc
 worker_thread+0x1a2/0x269
 ? pr_cont_work+0x58/0x58
 kthread+0xfa/0x10a
 ? pr_cont_work+0x58/0x58
 ? rcu_read_unlock_sched_notrace+0x48/0x48
 ret_from_fork+0x22/0x40

Signed-off-by: Yu Zhao <yuzhao@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/usb/smsc75xx.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/net/usb/smsc75xx.c
+++ b/drivers/net/usb/smsc75xx.c
@@ -1506,6 +1506,7 @@ static void smsc75xx_unbind(struct usbne
 {
 	struct smsc75xx_priv *pdata = (struct smsc75xx_priv *)(dev->data[0]);
 	if (pdata) {
+		cancel_work_sync(&pdata->set_multicast);
 		netif_dbg(dev, ifdown, dev->net, "free pdata\n");
 		kfree(pdata);
 		pdata = NULL;