[PATCH v3] rapidio: fix possible UAF when kfifo_alloc() fails

[Wang Weiyang <wangweiyang2@huawei.com>]

If kfifo_alloc() fails in mport_cdev_open(), goto err_fifo and just free
priv. But priv is still in the chdev->file_list, then list traversal
may cause UAF. This fixes the following smatch warning:

drivers/rapidio/devices/rio_mport_cdev.c:1930 mport_cdev_open() warn: '&priv->list' not removed from list

Fixes: e8de370188d0 ("rapidio: add mport char device driver")
Signed-off-by: Wang Weiyang <wangweiyang2@huawei.com>
---

Changes in v3:
- Avoid the list addition until the new instance has been fully
  initialized.

Changes in v2:
- Put the list addition after kfifo_alloc().

 drivers/rapidio/devices/rio_mport_cdev.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/rapidio/devices/rio_mport_cdev.c b/drivers/rapidio/devices/rio_mport_cdev.c
index 3cc83997a1f8..fecf523f36d8 100644
--- a/drivers/rapidio/devices/rio_mport_cdev.c
+++ b/drivers/rapidio/devices/rio_mport_cdev.c
@@ -1904,10 +1904,6 @@ static int mport_cdev_open(struct inode *inode, struct file *filp)
 
 	priv->md = chdev;
 
-	mutex_lock(&chdev->file_mutex);
-	list_add_tail(&priv->list, &chdev->file_list);
-	mutex_unlock(&chdev->file_mutex);
-
 	INIT_LIST_HEAD(&priv->db_filters);
 	INIT_LIST_HEAD(&priv->pw_filters);
 	spin_lock_init(&priv->fifo_lock);
@@ -1926,6 +1922,9 @@ static int mport_cdev_open(struct inode *inode, struct file *filp)
 	spin_lock_init(&priv->req_lock);
 	mutex_init(&priv->dma_lock);
 #endif
+	mutex_lock(&chdev->file_mutex);
+	list_add_tail(&priv->list, &chdev->file_list);
+	mutex_unlock(&chdev->file_mutex);
 
 	filp->private_data = priv;
 	goto out;
-- 
2.17.1