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media: cec: avoid decrementing transmit_queue_sz if it is 0
WARN if transmit_queue_sz is 0 but do not decrement it. The CEC adapter will become unresponsive if it goes below 0 since then it thinks there are 4 billion messages in the queue. Obviously this should not happen, but a driver bug could cause this. Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> Cc: <stable@vger.kernel.org> # for v4.12 and up Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
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01d4fb1154
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drivers/media/cec
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@ -380,7 +380,8 @@ static void cec_data_cancel(struct cec_data *data, u8 tx_status)
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} else {
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list_del_init(&data->list);
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if (!(data->msg.tx_status & CEC_TX_STATUS_OK))
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data->adap->transmit_queue_sz--;
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if (!WARN_ON(!data->adap->transmit_queue_sz))
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data->adap->transmit_queue_sz--;
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}
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if (data->msg.tx_status & CEC_TX_STATUS_OK) {
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@ -432,6 +433,14 @@ static void cec_flush(struct cec_adapter *adap)
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* need to do anything special in that case.
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*/
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}
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/*
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* If something went wrong and this counter isn't what it should
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* be, then this will reset it back to 0. Warn if it is not 0,
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* since it indicates a bug, either in this framework or in a
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* CEC driver.
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*/
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if (WARN_ON(adap->transmit_queue_sz))
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adap->transmit_queue_sz = 0;
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}
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/*
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@ -522,7 +531,8 @@ int cec_thread_func(void *_adap)
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data = list_first_entry(&adap->transmit_queue,
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struct cec_data, list);
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list_del_init(&data->list);
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adap->transmit_queue_sz--;
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if (!WARN_ON(!data->adap->transmit_queue_sz))
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adap->transmit_queue_sz--;
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/* Make this the current transmitting message */
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adap->transmitting = data;
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