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    Subject[PATCH AUTOSEL 4.14 09/17] usbnet: smsc95xx: Fix use-after-free after removal
    Date
    From: Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>

    [ Upstream commit b835a71ef64a61383c414d6bf2896d2c0161deca ]

    Syzbot reports an use-after-free in workqueue context:

    BUG: KASAN: use-after-free in mutex_unlock+0x19/0x40 kernel/locking/mutex.c:737
    mutex_unlock+0x19/0x40 kernel/locking/mutex.c:737
    __smsc95xx_mdio_read drivers/net/usb/smsc95xx.c:217 [inline]
    smsc95xx_mdio_read+0x583/0x870 drivers/net/usb/smsc95xx.c:278
    check_carrier+0xd1/0x2e0 drivers/net/usb/smsc95xx.c:644
    process_one_work+0x777/0xf90 kernel/workqueue.c:2274
    worker_thread+0xa8f/0x1430 kernel/workqueue.c:2420
    kthread+0x2df/0x300 kernel/kthread.c:255

    It looks like that smsc95xx_unbind() is freeing the structures that are
    still in use by the concurrently running workqueue callback. Thus switch
    to using cancel_delayed_work_sync() to ensure the work callback really
    is no longer active.

    Reported-by: syzbot+29dc7d4ae19b703ff947@syzkaller.appspotmail.com
    Signed-off-by: Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/net/usb/smsc95xx.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c
    index fc48da1c702d7..bcb99bee450a5 100644
    --- a/drivers/net/usb/smsc95xx.c
    +++ b/drivers/net/usb/smsc95xx.c
    @@ -1338,7 +1338,7 @@ static void smsc95xx_unbind(struct usbnet *dev, struct usb_interface *intf)
    struct smsc95xx_priv *pdata = (struct smsc95xx_priv *)(dev->data[0]);

    if (pdata) {
    - cancel_delayed_work(&pdata->carrier_check);
    + cancel_delayed_work_sync(&pdata->carrier_check);
    netif_dbg(dev, ifdown, dev->net, "free pdata\n");
    kfree(pdata);
    pdata = NULL;
    --
    2.25.1
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