Re: [Linux Kernel Bugs] KASAN: slab-use-after-free Read in cec_queue_msg_fh and 4 other crashes in the cec device (`cec_ioctl`)

[Hans Verkuil]

Hi Chenyuan,

Here is another patch for you to try. I think it is good for blocking CEC_ADAP_S_LOG_ADDRS
ioctl calls, but if the filehandle is in non-blocking mode, I'm still not certain it
is correct. But one issue at a time :-)

Regards,

	Hans

diff --git a/drivers/media/cec/core/cec-adap.c b/drivers/media/cec/core/cec-adap.c
index 559a172ebc6c..a493cbce2456 100644
--- a/drivers/media/cec/core/cec-adap.c
+++ b/drivers/media/cec/core/cec-adap.c
@@ -936,8 +936,7 @@ int cec_transmit_msg_fh(struct cec_adapter *adap, struct cec_msg *msg,
 	 */
 	mutex_unlock(&adap->lock);
 	wait_for_completion_killable(&data->c);
-	if (!data->completed)
-		cancel_delayed_work_sync(&data->work);
+	cancel_delayed_work_sync(&data->work);
 	mutex_lock(&adap->lock);

 	/* Cancel the transmit if it was interrupted */
@@ -1575,9 +1574,12 @@ static int cec_config_thread_func(void *arg)
  */
 static void cec_claim_log_addrs(struct cec_adapter *adap, bool block)
 {
-	if (WARN_ON(adap->is_configuring || adap->is_configured))
+	if (WARN_ON(adap->is_claiming_log_addrs ||
+		    adap->is_configuring || adap->is_configured))
 		return;

+	adap->is_claiming_log_addrs = true;
+
 	init_completion(&adap->config_completion);

 	/* Ready to kick off the thread */
@@ -1592,6 +1594,7 @@ static void cec_claim_log_addrs(struct cec_adapter *adap, bool block)
 		wait_for_completion(&adap->config_completion);
 		mutex_lock(&adap->lock);
 	}
+	adap->is_claiming_log_addrs = false;
 }

 /*
diff --git a/drivers/media/cec/core/cec-api.c b/drivers/media/cec/core/cec-api.c
index 67dc79ef1705..3ef915344304 100644
--- a/drivers/media/cec/core/cec-api.c
+++ b/drivers/media/cec/core/cec-api.c
@@ -178,7 +178,7 @@ static long cec_adap_s_log_addrs(struct cec_adapter *adap, struct cec_fh *fh,
 			   CEC_LOG_ADDRS_FL_ALLOW_RC_PASSTHRU |
 			   CEC_LOG_ADDRS_FL_CDC_ONLY;
 	mutex_lock(&adap->lock);
-	if (!adap->is_configuring &&
+	if (!adap->is_claiming_log_addrs && !adap->is_configuring &&
 	    (!log_addrs.num_log_addrs || !adap->is_configured) &&
 	    !cec_is_busy(adap, fh)) {
 		err = __cec_s_log_addrs(adap, &log_addrs, block);
@@ -664,6 +664,8 @@ static int cec_release(struct inode *inode, struct file *filp)
 		list_del_init(&data->xfer_list);
 	}
 	mutex_unlock(&adap->lock);
+
+	mutex_lock(&fh->lock);
 	while (!list_empty(&fh->msgs)) {
 		struct cec_msg_entry *entry =
 			list_first_entry(&fh->msgs, struct cec_msg_entry, list);
@@ -681,6 +683,7 @@ static int cec_release(struct inode *inode, struct file *filp)
 			kfree(entry);
 		}
 	}
+	mutex_unlock(&fh->lock);
 	kfree(fh);

 	cec_put_device(devnode);
diff --git a/include/media/cec.h b/include/media/cec.h
index 10c9cf6058b7..cc3fcd0496c3 100644
--- a/include/media/cec.h
+++ b/include/media/cec.h
@@ -258,6 +258,7 @@ struct cec_adapter {
 	u16 phys_addr;
 	bool needs_hpd;
 	bool is_enabled;
+	bool is_claiming_log_addrs;
 	bool is_configuring;
 	bool must_reconfigure;
 	bool is_configured;