6.4-stable review patch. If anyone has any objections, please let me know.
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From: Hans Verkuil hverkuil-cisco@xs4all.nl
[ Upstream commit da53c36ddd3f118a525a04faa8c47ca471e6c467 ]
A potential deadlock was found by Zheng Zhang with a local syzkaller instance.
The problem is that when a non-blocking CEC transmit is canceled by calling cec_data_cancel, that in turn can call the high-level received() driver callback, which can call cec_transmit_msg() to transmit a new message.
The cec_data_cancel() function is called with the adap->lock mutex held, and cec_transmit_msg() tries to take that same lock.
The root cause is that the received() callback can either be used to pass on a received message (and then adap->lock is not held), or to report a canceled transmit (and then adap->lock is held).
This is confusing, so create a new low-level adap_nb_transmit_canceled callback that reports back that a non-blocking transmit was canceled.
And the received() callback is only called when a message is received, as was the case before commit f9d0ecbf56f4 ("media: cec: correctly pass on reply results") complicated matters.
Reported-by: Zheng Zhang zheng.zhang@email.ucr.edu Signed-off-by: Hans Verkuil hverkuil-cisco@xs4all.nl Fixes: f9d0ecbf56f4 ("media: cec: correctly pass on reply results") Signed-off-by: Mauro Carvalho Chehab mchehab@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/media/cec/core/cec-adap.c | 4 ++-- include/media/cec.h | 6 ++++-- 2 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/drivers/media/cec/core/cec-adap.c b/drivers/media/cec/core/cec-adap.c index 241b1621b197c..a9b73fb33888d 100644 --- a/drivers/media/cec/core/cec-adap.c +++ b/drivers/media/cec/core/cec-adap.c @@ -385,8 +385,8 @@ static void cec_data_cancel(struct cec_data *data, u8 tx_status, u8 rx_status) cec_queue_msg_monitor(adap, &data->msg, 1);
if (!data->blocking && data->msg.sequence) - /* Allow drivers to process the message first */ - call_op(adap, received, &data->msg); + /* Allow drivers to react to a canceled transmit */ + call_void_op(adap, adap_nb_transmit_canceled, &data->msg);
cec_data_completed(data); } diff --git a/include/media/cec.h b/include/media/cec.h index abee41ae02d0e..6556cc161dc0a 100644 --- a/include/media/cec.h +++ b/include/media/cec.h @@ -121,14 +121,16 @@ struct cec_adap_ops { void (*adap_configured)(struct cec_adapter *adap, bool configured); int (*adap_transmit)(struct cec_adapter *adap, u8 attempts, u32 signal_free_time, struct cec_msg *msg); + void (*adap_nb_transmit_canceled)(struct cec_adapter *adap, + const struct cec_msg *msg); void (*adap_status)(struct cec_adapter *adap, struct seq_file *file); void (*adap_free)(struct cec_adapter *adap);
- /* Error injection callbacks */ + /* Error injection callbacks, called without adap->lock held */ int (*error_inj_show)(struct cec_adapter *adap, struct seq_file *sf); bool (*error_inj_parse_line)(struct cec_adapter *adap, char *line);
- /* High-level CEC message callback */ + /* High-level CEC message callback, called without adap->lock held */ int (*received)(struct cec_adapter *adap, struct cec_msg *msg); };