linux-kernel - [PATCH v2] rpmsg: char: Fix UAF and memory leak

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Message-Id: <20251112150108.49017-1-dawei.li@linux.dev>
Date: Wed, 12 Nov 2025 23:01:08 +0800
From: Dawei Li <dawei.li@...ux.dev>
To: andersson@...nel.org,
	mathieu.poirier@...aro.org
Cc: linux-remoteproc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	dawei.li@...ux.dev,
	set_pte_at@...look.com,
	Dan Carpenter <dan.carpenter@...aro.org>
Subject: [PATCH v2] rpmsg: char: Fix UAF and memory leak

Potential UAF and memory leak exsit in exception handling paths for
rpmsg_anonymous_eptdev_create(), fix them.

While at it, rework the error handling of rpmsg_eptdev_add() and its
callers, following rule of "release resource where it's allocated".

Fixes: 2410558f5f11 ("rpmsg: char: Implement eptdev based on anonymous inode")
Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
Closes: https://lore.kernel.org/all/aPi6gPZE2_ztOjIW@stanley.mountain/

Signed-off-by: Dawei Li <dawei.li@...ux.dev>
---
Change for v2:
- Add put_device() when __rpmsg_eptdev_open() failed.

Link to v1:
https://lore.kernel.org/all/20251112142813.33708-1-dawei.li@linux.dev/
---
 drivers/rpmsg/rpmsg_char.c | 61 +++++++++++++++++++++-----------------
 1 file changed, 34 insertions(+), 27 deletions(-)

diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c
index 34b35ea74aab..92c176e9b0e4 100644
--- a/drivers/rpmsg/rpmsg_char.c
+++ b/drivers/rpmsg/rpmsg_char.c
@@ -460,44 +460,34 @@ static int rpmsg_eptdev_add(struct rpmsg_eptdev *eptdev,
 
 	eptdev->chinfo = chinfo;
 
-	if (cdev) {
-		ret = ida_alloc_max(&rpmsg_minor_ida, RPMSG_DEV_MAX - 1, GFP_KERNEL);
-		if (ret < 0)
-			goto free_eptdev;
-
-		dev->devt = MKDEV(MAJOR(rpmsg_major), ret);
-	}
-
 	/* Anonymous inode device still need device name for dev_err() and friends */
 	ret = ida_alloc(&rpmsg_ept_ida, GFP_KERNEL);
 	if (ret < 0)
-		goto free_minor_ida;
+		return ret;
 	dev->id = ret;
 	dev_set_name(dev, "rpmsg%d", ret);
 
-	ret = 0;
-
 	if (cdev) {
+		ret = ida_alloc_max(&rpmsg_minor_ida, RPMSG_DEV_MAX - 1, GFP_KERNEL);
+		if (ret < 0) {
+			ida_free(&rpmsg_ept_ida, dev->id);
+			return ret;
+		}
+
+		dev->devt = MKDEV(MAJOR(rpmsg_major), ret);
+
 		ret = cdev_device_add(&eptdev->cdev, &eptdev->dev);
-		if (ret)
-			goto free_ept_ida;
+		if (ret) {
+			ida_free(&rpmsg_ept_ida, dev->id);
+			ida_free(&rpmsg_minor_ida, MINOR(dev->devt));
+			return ret;
+		}
 	}
 
 	/* We can now rely on the release function for cleanup */
 	dev->release = rpmsg_eptdev_release_device;
 
-	return ret;
-
-free_ept_ida:
-	ida_free(&rpmsg_ept_ida, dev->id);
-free_minor_ida:
-	if (cdev)
-		ida_free(&rpmsg_minor_ida, MINOR(dev->devt));
-free_eptdev:
-	put_device(dev);
-	kfree(eptdev);
-
-	return ret;
+	return 0;
 }
 
 static int rpmsg_chrdev_eptdev_add(struct rpmsg_eptdev *eptdev, struct rpmsg_channel_info chinfo)
@@ -509,12 +499,17 @@ int rpmsg_chrdev_eptdev_create(struct rpmsg_device *rpdev, struct device *parent
 			       struct rpmsg_channel_info chinfo)
 {
 	struct rpmsg_eptdev *eptdev;
+	int ret;
 
 	eptdev = rpmsg_chrdev_eptdev_alloc(rpdev, parent);
 	if (IS_ERR(eptdev))
 		return PTR_ERR(eptdev);
 
-	return rpmsg_chrdev_eptdev_add(eptdev, chinfo);
+	ret = rpmsg_chrdev_eptdev_add(eptdev, chinfo);
+	if (ret)
+		kfree(eptdev);
+
+	return ret;
 }
 EXPORT_SYMBOL(rpmsg_chrdev_eptdev_create);
 
@@ -546,6 +541,11 @@ int rpmsg_anonymous_eptdev_create(struct rpmsg_device *rpdev, struct device *par
 	ret =  rpmsg_eptdev_add(eptdev, chinfo, false);
 	if (ret) {
 		dev_err(&eptdev->dev, "failed to add %s\n", eptdev->chinfo.name);
+		/*
+		 * Avoid put_device() or WARN() will be triggered due to absence of
+		 * device::release(), refer to device_release().
+		 */
+		kfree(eptdev);
 		return ret;
 	}
 
@@ -561,6 +561,8 @@ int rpmsg_anonymous_eptdev_create(struct rpmsg_device *rpdev, struct device *par
 
 	if (!ret)
 		*pfd = fd;
+	else
+		put_device(&eptdev->dev);
 
 	return ret;
 }
@@ -571,6 +573,7 @@ static int rpmsg_chrdev_probe(struct rpmsg_device *rpdev)
 	struct rpmsg_channel_info chinfo;
 	struct rpmsg_eptdev *eptdev;
 	struct device *dev = &rpdev->dev;
+	int ret;
 
 	memcpy(chinfo.name, rpdev->id.name, RPMSG_NAME_SIZE);
 	chinfo.src = rpdev->src;
@@ -589,7 +592,11 @@ static int rpmsg_chrdev_probe(struct rpmsg_device *rpdev)
 	 */
 	eptdev->default_ept->priv = eptdev;
 
-	return rpmsg_chrdev_eptdev_add(eptdev, chinfo);
+	ret = rpmsg_chrdev_eptdev_add(eptdev, chinfo);
+	if (ret)
+		kfree(eptdev);
+
+	return ret;
 }
 
 static void rpmsg_chrdev_remove(struct rpmsg_device *rpdev)
-- 
2.25.1