From 26e5eab93db02f82fd24ff76ce363958c6433936 Mon Sep 17 00:00:00 2001 From: Hans Verkuil Date: Sat, 7 Dec 2019 23:48:09 +0100 Subject: [PATCH] media: cec: avoid decrementing transmit_queue_sz if it is 0 commit 95c29d46ab2a517e4c26d0a07300edca6768db17 upstream. 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 Cc: # for v4.12 and up Signed-off-by: Mauro Carvalho Chehab Signed-off-by: Greg Kroah-Hartman --- drivers/media/cec/cec-adap.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/drivers/media/cec/cec-adap.c b/drivers/media/cec/cec-adap.c index 8030485ecfd7..0d7d687aeea0 100644 --- a/drivers/media/cec/cec-adap.c +++ b/drivers/media/cec/cec-adap.c @@ -330,7 +330,8 @@ static void cec_data_cancel(struct cec_data *data) } 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--; } /* Mark it as an error */ @@ -377,6 +378,14 @@ 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; } /* @@ -465,7 +474,8 @@ 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;