fcntl: fix potential deadlock for &fasync_struct.fa_lock
stable inclusion from linux-4.19.207 commit 64dd1fbb0bb743ccd2fb420c441f4ca9732f598f -------------------------------- [ Upstream commit 2f488f69 ] There is an existing lock hierarchy of &dev->event_lock --> &fasync_struct.fa_lock --> &f->f_owner.lock from the following call chain: input_inject_event(): spin_lock_irqsave(&dev->event_lock,...); input_handle_event(): input_pass_values(): input_to_handler(): evdev_events(): evdev_pass_values(): spin_lock(&client->buffer_lock); __pass_event(): kill_fasync(): kill_fasync_rcu(): read_lock(&fa->fa_lock); send_sigio(): read_lock_irqsave(&fown->lock,...); &dev->event_lock is HARDIRQ-safe, so interrupts have to be disabled while grabbing &fasync_struct.fa_lock, otherwise we invert the lock hierarchy. However, since kill_fasync which calls kill_fasync_rcu is an exported symbol, it may not necessarily be called with interrupts disabled. As kill_fasync_rcu may be called with interrupts disabled (for example, in the call chain above), we replace calls to read_lock/read_unlock on &fasync_struct.fa_lock in kill_fasync_rcu with read_lock_irqsave/read_unlock_irqrestore. Signed-off-by: NDesmond Cheong Zhi Xi <desmondcheongzx@gmail.com> Signed-off-by: NJeff Layton <jlayton@kernel.org> Signed-off-by: NSasha Levin <sashal@kernel.org> Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
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