Patch "rpmsg: char: Add mutex protection for rpmsg_eptdev_open()" has been added to the 5.18-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    rpmsg: char: Add mutex protection for rpmsg_eptdev_open()

to the 5.18-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     rpmsg-char-add-mutex-protection-for-rpmsg_eptdev_ope.patch
and it can be found in the queue-5.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit d6c7f8f38c224c1433b0152d9602316a5667ff51
Author: Shengjiu Wang <shengjiu.wang@xxxxxxx>
Date:   Sat May 21 11:35:05 2022 +0800

    rpmsg: char: Add mutex protection for rpmsg_eptdev_open()
    
    [ Upstream commit abe13e9a561d6b3e82b21362c0d6dd3ecd8a5b13 ]
    
    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,the return state
    may be success or EBUSY.
    
    Fixes: 964e8bedd5a1 ("rpmsg: char: Return an error if device already open")
    Signed-off-by: Shengjiu Wang <shengjiu.wang@xxxxxxx>
    Link: https://lore.kernel.org/r/1653104105-16779-1-git-send-email-shengjiu.wang@xxxxxxx
    Signed-off-by: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

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;
 }