[PATCH 1/1] net: qrtr: start MHI channel after endpoit creation

[PATCH 1/1] net: qrtr: start MHI channel after endpoit creation

[Maxim Kochetkov]

MHI channel may generates event/interrupt right after enabling.
It may leads to 2 race conditions issues.

1)
Such event may be dropped by qcom_mhi_qrtr_dl_callback() at check:

	if (!qdev || mhi_res->transaction_status)
		return;

Because dev_set_drvdata(&mhi_dev->dev, qdev) may be not performed at
this moment. In this situation qrtr-ns will be unable to enumerate
services in device.
---------------------------------------------------------------

2)
Such event may come at the moment after dev_set_drvdata() and
before qrtr_endpoint_register(). In this case kernel will panic with
accessing wrong pointer at qcom_mhi_qrtr_dl_callback():

	rc = qrtr_endpoint_post(&qdev->ep, mhi_res->buf_addr,
				mhi_res->bytes_xferd);

Because endpoint is not created yet.
--------------------------------------------------------------
So move mhi_prepare_for_transfer_autoqueue after endpoint creation
to fix it.

Fixes: a2e2cc0dbb11 ("net: qrtr: Start MHI channels during init")
Signed-off-by: Maxim Kochetkov <fido_max@inbox.ru>
Reviewed-by: Hemant Kumar <quic_hemantk@quicinc.com>
Reviewed-by: Manivannan Sadhasivam <mani@kernel.org>
---
 net/qrtr/mhi.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/net/qrtr/mhi.c b/net/qrtr/mhi.c
index 18196e1c8c2f..17520d9e7a51 100644
--- a/net/qrtr/mhi.c
+++ b/net/qrtr/mhi.c
@@ -78,11 +78,6 @@ static int qcom_mhi_qrtr_probe(struct mhi_device *mhi_dev,
 	struct qrtr_mhi_dev *qdev;
 	int rc;
 
-	/* start channels */
-	rc = mhi_prepare_for_transfer_autoqueue(mhi_dev);
-	if (rc)
-		return rc;
-
 	qdev = devm_kzalloc(&mhi_dev->dev, sizeof(*qdev), GFP_KERNEL);
 	if (!qdev)
 		return -ENOMEM;
@@ -96,6 +91,11 @@ static int qcom_mhi_qrtr_probe(struct mhi_device *mhi_dev,
 	if (rc)
 		return rc;
 
+	/* start channels */
+	rc = mhi_prepare_for_transfer_autoqueue(mhi_dev);
+	if (rc)
+		return rc;
+
 	dev_dbg(qdev->dev, "Qualcomm MHI QRTR driver probed\n");
 
 	return 0;
-- 
2.34.1

Re: [PATCH 1/1] net: qrtr: start MHI channel after endpoit creation

[Manivannan Sadhasivam]

On Thu, Aug 11, 2022 at 12:21:45PM +0300, Maxim Kochetkov wrote:
> MHI channel may generates event/interrupt right after enabling.
> It may leads to 2 race conditions issues.
> 
> 1)
> Such event may be dropped by qcom_mhi_qrtr_dl_callback() at check:
> 
> 	if (!qdev || mhi_res->transaction_status)
> 		return;
> 
> Because dev_set_drvdata(&mhi_dev->dev, qdev) may be not performed at
> this moment. In this situation qrtr-ns will be unable to enumerate
> services in device.
> ---------------------------------------------------------------
> 
> 2)
> Such event may come at the moment after dev_set_drvdata() and
> before qrtr_endpoint_register(). In this case kernel will panic with
> accessing wrong pointer at qcom_mhi_qrtr_dl_callback():
> 
> 	rc = qrtr_endpoint_post(&qdev->ep, mhi_res->buf_addr,
> 				mhi_res->bytes_xferd);
> 
> Because endpoint is not created yet.
> --------------------------------------------------------------
> So move mhi_prepare_for_transfer_autoqueue after endpoint creation
> to fix it.
> 
> Fixes: a2e2cc0dbb11 ("net: qrtr: Start MHI channels during init")
> Signed-off-by: Maxim Kochetkov <fido_max@inbox.ru>
> Reviewed-by: Hemant Kumar <quic_hemantk@quicinc.com>
> Reviewed-by: Manivannan Sadhasivam <mani@kernel.org>
> ---
>  net/qrtr/mhi.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/net/qrtr/mhi.c b/net/qrtr/mhi.c
> index 18196e1c8c2f..17520d9e7a51 100644
> --- a/net/qrtr/mhi.c
> +++ b/net/qrtr/mhi.c
> @@ -78,11 +78,6 @@ static int qcom_mhi_qrtr_probe(struct mhi_device *mhi_dev,
>  	struct qrtr_mhi_dev *qdev;
>  	int rc;
>  
> -	/* start channels */
> -	rc = mhi_prepare_for_transfer_autoqueue(mhi_dev);
> -	if (rc)
> -		return rc;
> -
>  	qdev = devm_kzalloc(&mhi_dev->dev, sizeof(*qdev), GFP_KERNEL);
>  	if (!qdev)
>  		return -ENOMEM;
> @@ -96,6 +91,11 @@ static int qcom_mhi_qrtr_probe(struct mhi_device *mhi_dev,
>  	if (rc)
>  		return rc;
>  
> +	/* start channels */
> +	rc = mhi_prepare_for_transfer_autoqueue(mhi_dev);
> +	if (rc)
> +		return rc;

I missed the fact that you need to call qrtr_endpoint_unregister() in
the error path.

Please fix it.

Thanks,
Mani

> +
>  	dev_dbg(qdev->dev, "Qualcomm MHI QRTR driver probed\n");
>  
>  	return 0;
> -- 
> 2.34.1
>