linux-kernel - [PATCH] rpmsg: char: Add mutex protection for rpmsg_eptdev

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Date:   Mon, 28 Mar 2022 14:31:11 +0800
From:   Shengjiu Wang <shengjiu.wang@....com>
To:     bjorn.andersson@...aro.org, mathieu.poirier@...aro.org
Cc:     linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org,
        shengjiu.wang@...il.com
Subject: [PATCH] rpmsg: char: Add mutex protection for rpmsg_eptdev_open()

There is no mutex protection for rpmsg_eptdev_open(),
especially for eptdev->ept read and write operation.
It may cause issues when multiple instances call
rpmsg_eptdev_open() in parallel,

Signed-off-by: Shengjiu Wang <shengjiu.wang@....com>
---
 drivers/rpmsg/rpmsg_char.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c
index b6183d4f62a2..4f2189111494 100644
--- a/drivers/rpmsg/rpmsg_char.c
+++ b/drivers/rpmsg/rpmsg_char.c
@@ -120,8 +120,11 @@ static int rpmsg_eptdev_open(struct inode *inode, struct file *filp)
 	struct rpmsg_device *rpdev = eptdev->rpdev;
 	struct device *dev = &eptdev->dev;
 
-	if (eptdev->ept)
+	mutex_lock(&eptdev->ept_lock);
+	if (eptdev->ept) {
+		mutex_unlock(&eptdev->ept_lock);
 		return -EBUSY;
+	}
 
 	get_device(dev);
 
@@ -137,11 +140,13 @@ static int rpmsg_eptdev_open(struct inode *inode, struct file *filp)
 	if (!ept) {
 		dev_err(dev, "failed to open %s\n", eptdev->chinfo.name);
 		put_device(dev);
+		mutex_unlock(&eptdev->ept_lock);
 		return -EINVAL;
 	}
 
 	eptdev->ept = ept;
 	filp->private_data = eptdev;
+	mutex_unlock(&eptdev->ept_lock);
 
 	return 0;
 }
-- 
2.17.1