cec: safely unhook lists in cec_data

Commit Message

Hans Verkuil Nov. 24, 2021, 10:38 a.m. UTC

smatch warns about data->list not being removed from list:

drivers/media/cec/core/cec-adap.c:926 cec_transmit_msg_fh() warn: '&data->list' not removed from list

It is a false warning, but it doesn't hurt to make the code more robust
and safely unhook data->list and data->xfer_list together with a WARN_ON
if this is actually ever needed (this really shouldn't happen).

Note that fixing the data->list warning just replaced it with a new similar warning
for data->xfer_list, so both needed to be addressed.

Signed-off-by: Hans Verkuil <[e-mail]>
---
 drivers/media/cec/core/cec-adap.c | 8 +++++++-
 drivers/media/cec/core/cec-api.c  | 2 +-
 2 files changed, 8 insertions(+), 2 deletions(-)

Patch

diff --git a/drivers/media/cec/core/cec-adap.c b/drivers/media/cec/core/cec-adap.c
index 79fa36de8a04..3eea1d6a9308 100644
--- a/drivers/media/cec/core/cec-adap.c
+++ b/drivers/media/cec/core/cec-adap.c
@@ -342,7 +342,7 @@  static void cec_data_completed(struct cec_data *data)
 	 * Without that we would be referring to a closed filehandle.
 	 */
 	if (data->fh)
-		list_del(&data->xfer_list);
+		list_del_init(&data->xfer_list);

 	if (data->blocking) {
 		/*
@@ -898,6 +898,8 @@  int cec_transmit_msg_fh(struct cec_adapter *adap, struct cec_msg *msg,

 	if (fh)
 		list_add_tail(&data->xfer_list, &fh->xfer_list);
+	else
+		INIT_LIST_HEAD(&data->xfer_list);

 	list_add_tail(&data->list, &adap->transmit_queue);
 	adap->transmit_queue_sz++;
@@ -923,6 +925,10 @@  int cec_transmit_msg_fh(struct cec_adapter *adap, struct cec_msg *msg,

 	/* The transmit completed (possibly with an error) */
 	*msg = data->msg;
+	if (WARN_ON(!list_empty(&data->list)))
+		list_del(&data->list);
+	if (WARN_ON(!list_empty(&data->xfer_list)))
+		list_del(&data->xfer_list);
 	kfree(data);
 	return 0;
 }
diff --git a/drivers/media/cec/core/cec-api.c b/drivers/media/cec/core/cec-api.c
index 769e6b4cddce..0edb7142afdb 100644
--- a/drivers/media/cec/core/cec-api.c
+++ b/drivers/media/cec/core/cec-api.c
@@ -669,7 +669,7 @@  static int cec_release(struct inode *inode, struct file *filp)

 		data->blocking = false;
 		data->fh = NULL;
-		list_del(&data->xfer_list);
+		list_del_init(&data->xfer_list);
 	}
 	mutex_unlock(&adap->lock);
 	while (!list_empty(&fh->msgs)) {