linux-kernel - [PATCH 2/3] habanalabs: initialize hpriv fields before adding new node

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Date:   Tue, 12 Oct 2021 16:40:50 +0300
From:   Oded Gabbay <ogabbay@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     Moti Haimovski <mhaimovski@...ana.ai>
Subject: [PATCH 2/3] habanalabs: initialize hpriv fields before adding new node

From: Moti Haimovski <mhaimovski@...ana.ai>

When adding a new node to the hpriv list, the driver should
initialize its fields before adding the new node.

Otherwise, there may be some small chance of another thread traversing
that list and accessing the new node's fields without them being
initialized.

Signed-off-by: Moti Haimovski <mhaimovski@...ana.ai>
Reviewed-by: Oded Gabbay <ogabbay@...nel.org>
Signed-off-by: Oded Gabbay <ogabbay@...nel.org>
---
 .../misc/habanalabs/common/habanalabs_drv.c   | 23 ++++++++++++-------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/drivers/misc/habanalabs/common/habanalabs_drv.c b/drivers/misc/habanalabs/common/habanalabs_drv.c
index 1da56069750a..949d1b5c5c41 100644
--- a/drivers/misc/habanalabs/common/habanalabs_drv.c
+++ b/drivers/misc/habanalabs/common/habanalabs_drv.c
@@ -225,6 +225,17 @@ int hl_device_open_ctrl(struct inode *inode, struct file *filp)
 	if (!hpriv)
 		return -ENOMEM;
 
+	/* Prevent other routines from reading partial hpriv data by
+	 * initializing hpriv fields before inserting it to the list
+	 */
+	hpriv->hdev = hdev;
+	filp->private_data = hpriv;
+	hpriv->filp = filp;
+	hpriv->is_control = true;
+	nonseekable_open(inode, filp);
+
+	hpriv->taskpid = find_get_pid(current->pid);
+
 	mutex_lock(&hdev->fpriv_list_lock);
 
 	if (!hl_device_operational(hdev, NULL)) {
@@ -238,19 +249,15 @@ int hl_device_open_ctrl(struct inode *inode, struct file *filp)
 	list_add(&hpriv->dev_node, &hdev->fpriv_list);
 	mutex_unlock(&hdev->fpriv_list_lock);
 
-	hpriv->hdev = hdev;
-	filp->private_data = hpriv;
-	hpriv->filp = filp;
-	hpriv->is_control = true;
-	nonseekable_open(inode, filp);
-
-	hpriv->taskpid = find_get_pid(current->pid);
-
 	return 0;
 
 out_err:
 	mutex_unlock(&hdev->fpriv_list_lock);
+	filp->private_data = NULL;
+	put_pid(hpriv->taskpid);
+
 	kfree(hpriv);
+
 	return rc;
 }
 
-- 
2.17.1