linux-kernel - [PATCH 5.15 066/177] net: hns3: fix race condition in debugfs

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Message-Id: <20211220143042.322618218@linuxfoundation.org>
Date:   Mon, 20 Dec 2021 15:33:36 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Yufeng Mo <moyufeng@...wei.com>,
        Guangbin Huang <huangguangbin2@...wei.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 066/177] net: hns3: fix race condition in debugfs

From: Yufeng Mo <moyufeng@...wei.com>

[ Upstream commit 6dde452bceca3f2ed2b33bc46a16ff5682a03a2e ]

When multiple threads concurrently access the debugfs content, data
and pointer exceptions may occur. Therefore, mutex lock protection is
added for debugfs.

Fixes: 5e69ea7ee2a6 ("net: hns3: refactor the debugfs process")
Signed-off-by: Yufeng Mo <moyufeng@...wei.com>
Signed-off-by: Guangbin Huang <huangguangbin2@...wei.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/ethernet/hisilicon/hns3/hnae3.h   |  2 ++
 .../ethernet/hisilicon/hns3/hns3_debugfs.c    | 20 +++++++++++++------
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/hisilicon/hns3/hnae3.h b/drivers/net/ethernet/hisilicon/hns3/hnae3.h
index d701451596c82..47bba4c62f040 100644
--- a/drivers/net/ethernet/hisilicon/hns3/hnae3.h
+++ b/drivers/net/ethernet/hisilicon/hns3/hnae3.h
@@ -830,6 +830,8 @@ struct hnae3_handle {
 
 	u8 netdev_flags;
 	struct dentry *hnae3_dbgfs;
+	/* protects concurrent contention between debugfs commands */
+	struct mutex dbgfs_lock;
 
 	/* Network interface message level enabled bits */
 	u32 msg_enable;
diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3_debugfs.c b/drivers/net/ethernet/hisilicon/hns3/hns3_debugfs.c
index e54f96251fea9..3205849bdb95b 100644
--- a/drivers/net/ethernet/hisilicon/hns3/hns3_debugfs.c
+++ b/drivers/net/ethernet/hisilicon/hns3/hns3_debugfs.c
@@ -1021,6 +1021,7 @@ static ssize_t hns3_dbg_read(struct file *filp, char __user *buffer,
 	if (ret)
 		return ret;
 
+	mutex_lock(&handle->dbgfs_lock);
 	save_buf = &hns3_dbg_cmd[index].buf;
 
 	if (!test_bit(HNS3_NIC_STATE_INITED, &priv->state) ||
@@ -1033,15 +1034,15 @@ static ssize_t hns3_dbg_read(struct file *filp, char __user *buffer,
 		read_buf = *save_buf;
 	} else {
 		read_buf = kvzalloc(hns3_dbg_cmd[index].buf_len, GFP_KERNEL);
-		if (!read_buf)
-			return -ENOMEM;
+		if (!read_buf) {
+			ret = -ENOMEM;
+			goto out;
+		}
 
 		/* save the buffer addr until the last read operation */
 		*save_buf = read_buf;
-	}
 
-	/* get data ready for the first time to read */
-	if (!*ppos) {
+		/* get data ready for the first time to read */
 		ret = hns3_dbg_read_cmd(dbg_data, hns3_dbg_cmd[index].cmd,
 					read_buf, hns3_dbg_cmd[index].buf_len);
 		if (ret)
@@ -1050,8 +1051,10 @@ static ssize_t hns3_dbg_read(struct file *filp, char __user *buffer,
 
 	size = simple_read_from_buffer(buffer, count, ppos, read_buf,
 				       strlen(read_buf));
-	if (size > 0)
+	if (size > 0) {
+		mutex_unlock(&handle->dbgfs_lock);
 		return size;
+	}
 
 out:
 	/* free the buffer for the last read operation */
@@ -1060,6 +1063,7 @@ static ssize_t hns3_dbg_read(struct file *filp, char __user *buffer,
 		*save_buf = NULL;
 	}
 
+	mutex_unlock(&handle->dbgfs_lock);
 	return ret;
 }
 
@@ -1132,6 +1136,8 @@ int hns3_dbg_init(struct hnae3_handle *handle)
 			debugfs_create_dir(hns3_dbg_dentry[i].name,
 					   handle->hnae3_dbgfs);
 
+	mutex_init(&handle->dbgfs_lock);
+
 	for (i = 0; i < ARRAY_SIZE(hns3_dbg_cmd); i++) {
 		if ((hns3_dbg_cmd[i].cmd == HNAE3_DBG_CMD_TM_NODES &&
 		     ae_dev->dev_version <= HNAE3_DEVICE_VERSION_V2) ||
@@ -1158,6 +1164,7 @@ int hns3_dbg_init(struct hnae3_handle *handle)
 	return 0;
 
 out:
+	mutex_destroy(&handle->dbgfs_lock);
 	debugfs_remove_recursive(handle->hnae3_dbgfs);
 	handle->hnae3_dbgfs = NULL;
 	return ret;
@@ -1173,6 +1180,7 @@ void hns3_dbg_uninit(struct hnae3_handle *handle)
 			hns3_dbg_cmd[i].buf = NULL;
 		}
 
+	mutex_destroy(&handle->dbgfs_lock);
 	debugfs_remove_recursive(handle->hnae3_dbgfs);
 	handle->hnae3_dbgfs = NULL;
 }
-- 
2.33.0