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From:   Deepak Kumar Singh <quic_deesin@quicinc.com>
To:     <bjorn.andersson@linaro.org>, <swboyd@chromium.org>,
        <quic_clew@quicinc.com>, <mathieu.poirier@linaro.org>
CC:     <linux-kernel@vger.kernel.org>, <linux-arm-msm@vger.kernel.org>,
        <linux-remoteproc@vger.kernel.org>,
        Deepak Kumar Singh <quic_deesin@quicinc.com>
Subject: [PATCH V2 2/2] rpmsg: glink: Add lock to rpmsg_ctrldev_remove
Date:   Tue, 6 Sep 2022 00:25:20 +0530
Message-ID: <1662404120-24338-2-git-send-email-quic_deesin@quicinc.com>
In-Reply-To: <1662404120-24338-1-git-send-email-quic_deesin@quicinc.com>
References: <1662404120-24338-1-git-send-email-quic_deesin@quicinc.com>
MIME-Version: 1.0
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Hold ctrl device lock in rpmsg_ctrldev_remove to avoid any
new create ept call to proceed, otherwise new ept creation
and associted char device may suceed. Any further call from
user space for rpmsg_eptdev_open will reference already freed
rpdev and will result in crash. Below crash signature was
observed -

rpmsg_create_ept+0x40/0xa0
rpmsg_eptdev_open+0x88/0x138
chrdev_open+0xc4/0x1c8
do_dentry_open+0x230/0x378
vfs_open+0x3c/0x48
path_openat+0x93c/0xa78
do_filp_open+0x98/0x118
do_sys_openat2+0x90/0x220
do_sys_open+0x64/0x8c

Signed-off-by: Deepak Kumar Singh <quic_deesin@quicinc.com>
---
 drivers/rpmsg/rpmsg_ctrl.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/rpmsg/rpmsg_ctrl.c b/drivers/rpmsg/rpmsg_ctrl.c
index 107da70..4332538 100644
--- a/drivers/rpmsg/rpmsg_ctrl.c
+++ b/drivers/rpmsg/rpmsg_ctrl.c
@@ -194,10 +194,12 @@ static void rpmsg_ctrldev_remove(struct rpmsg_device *rpdev)
 	struct rpmsg_ctrldev *ctrldev = dev_get_drvdata(&rpdev->dev);
 	int ret;
 
+	mutex_lock(&ctrldev->ctrl_lock);
 	/* Destroy all endpoints */
 	ret = device_for_each_child(&ctrldev->dev, NULL, rpmsg_chrdev_eptdev_destroy);
 	if (ret)
 		dev_warn(&rpdev->dev, "failed to nuke endpoints: %d\n", ret);
+	mutex_unlock(&ctrldev->ctrl_lock);
 
 	cdev_device_del(&ctrldev->cdev, &ctrldev->dev);
 	put_device(&ctrldev->dev);
-- 
2.7.4