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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>
This commit is contained in:
Hans Verkuil 2019-12-07 23:48:09 +01:00 committed by Mauro Carvalho Chehab
parent 01d4fb1154
commit 4be77174c3
1 changed files with 12 additions and 2 deletions
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14
drivers/media/cec/cec-adap.c
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@ -380,7 +380,8 @@ static void cec_data_cancel(struct cec_data *data, u8 tx_status)
} else {
list_del_init(&data->list);
if (!(data->msg.tx_status & CEC_TX_STATUS_OK))
data->adap->transmit_queue_sz--;
if (!WARN_ON(!data->adap->transmit_queue_sz))
data->adap->transmit_queue_sz--;
}
if (data->msg.tx_status & CEC_TX_STATUS_OK) {
@ -432,6 +433,14 @@ static void cec_flush(struct cec_adapter *adap)
* need to do anything special in that case.
*/
}
/*
* If something went wrong and this counter isn't what it should
* be, then this will reset it back to 0. Warn if it is not 0,
* since it indicates a bug, either in this framework or in a
* CEC driver.
*/
if (WARN_ON(adap->transmit_queue_sz))
adap->transmit_queue_sz = 0;
}
/*
@ -522,7 +531,8 @@ int cec_thread_func(void *_adap)
data = list_first_entry(&adap->transmit_queue,
struct cec_data, list);
list_del_init(&data->list);
adap->transmit_queue_sz--;
if (!WARN_ON(!data->adap->transmit_queue_sz))
adap->transmit_queue_sz--;
/* Make this the current transmitting message */
adap->transmitting = data;