linux-kernel - [PATCH V1 1/3] rpmsg: glink: Free device context only when cdev not in use

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Date:   Thu, 27 Jan 2022 00:34:44 +0530
From:   Deepak Kumar Singh <quic_deesin@...cinc.com>
To:     <bjorn.andersson@...aro.org>, <swboyd@...omium.org>,
        <quic_clew@...cinc.com>, <mathieu.poirier@...aro.org>
CC:     <linux-kernel@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-remoteproc@...r.kernel.org>,
        Deepak Kumar Singh <quic_deesin@...cinc.com>,
        Ohad Ben-Cohen <ohad@...ery.com>
Subject: [PATCH V1 1/3] rpmsg: glink: Free device context only when cdev not in use

Struct device holding cdev should not be freed unless cdev
is not in use. It is possible that user space has opened
char device while kernel has freed the associated struct
device context.

Mark dev kobj as parent of cdev, so that chardev_add gets
an extra reference to dev. This ensures device context is not
freed until cdev is is not in uses.
---
 drivers/rpmsg/rpmsg_char.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c
index c03a118..72ee101 100644
--- a/drivers/rpmsg/rpmsg_char.c
+++ b/drivers/rpmsg/rpmsg_char.c
@@ -417,6 +417,7 @@ static int rpmsg_eptdev_create(struct rpmsg_ctrldev *ctrldev,
 	dev->id = ret;
 	dev_set_name(dev, "rpmsg%d", ret);
 
+	cdev_set_parent(&eptdev->cdev, &dev->kobj);
 	ret = cdev_add(&eptdev->cdev, dev->devt, 1);
 	if (ret)
 		goto free_ept_ida;
@@ -533,6 +534,7 @@ static int rpmsg_chrdev_probe(struct rpmsg_device *rpdev)
 	dev->id = ret;
 	dev_set_name(&ctrldev->dev, "rpmsg_ctrl%d", ret);
 
+	cdev_set_parent(&ctrldev->cdev, &dev->kobj);
 	ret = cdev_add(&ctrldev->cdev, dev->devt, 1);
 	if (ret)
 		goto free_ctrl_ida;
-- 
2.7.4