linux-kernel - [PATCH v2] rapidio: fix possible UAF when kfifo

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Message-ID: <20221119040335.46794-1-wangweiyang2@huawei.com>
Date:   Sat, 19 Nov 2022 12:03:35 +0800
From:   Wang Weiyang <wangweiyang2@...wei.com>
To:     <mporter@...nel.crashing.org>, <alex.bou9@...il.com>,
        <akpm@...ux-foundation.org>, <yangyingliang@...wei.com>,
        <jakobkoschel@...il.com>, <jhubbard@...dia.com>,
        <error27@...il.com>, <wangweiyang2@...wei.com>
CC:     <linux-kernel@...r.kernel.org>
Subject: [PATCH v2] rapidio: fix possible UAF when kfifo_alloc() fails

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@...wei.com>
---
Changes in v2:
- Avoid adding the new instance onto the list until the new instance
  has been fully initialized.

 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..86b28c4cd906 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);
@@ -1920,6 +1916,9 @@ static int mport_cdev_open(struct inode *inode, struct file *filp)
 		ret = -ENOMEM;
 		goto err_fifo;
 	}
+	mutex_lock(&chdev->file_mutex);
+	list_add_tail(&priv->list, &chdev->file_list);
+	mutex_unlock(&chdev->file_mutex);
 
 #ifdef CONFIG_RAPIDIO_DMA_ENGINE
 	INIT_LIST_HEAD(&priv->async_list);
-- 
2.17.1