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SubjectRe: [PATCH] usbnet: smsc95xx: Fix use-after-free after removal
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From: Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
Date: Sun, 21 Jun 2020 13:43:26 +0300

> 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 is no longer active.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>

Applied, thanks.

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