linux-kernel - [PATCH V1] extcon: modify extcon device to be created after driver data is set

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Message-Id: <20220427030005.706-1-bw365.lee@samsung.com>
Date:   Wed, 27 Apr 2022 12:00:05 +0900
From:   bumwoo lee <bw365.lee@...sung.com>
To:     MyungJoo Ham <myungjoo.ham@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        linux-kernel@...r.kernel.org
Cc:     bumwoo lee <bw365.lee@...sung.com>
Subject: [PATCH V1] extcon: modify extcon device to be created after driver
 data is set

Currently, someone can invoke the sysfs such as state_show()
intermittently before dev_set_drvdata() is done.
And it can be a cause of kernel Oops because of edev is Null at that time.
So modified the driver registration to after setting drviver data.

- Oops's backtrace.

Backtrace:
[<c067865c>] (state_show) from [<c05222e8>] (dev_attr_show)
[<c05222c0>] (dev_attr_show) from [<c02c66e0>] (sysfs_kf_seq_show)
[<c02c6648>] (sysfs_kf_seq_show) from [<c02c496c>] (kernfs_seq_show)
[<c02c4938>] (kernfs_seq_show) from [<c025e2a0>] (seq_read)
[<c025e11c>] (seq_read) from [<c02c50a0>] (kernfs_fop_read)
[<c02c5064>] (kernfs_fop_read) from [<c0231cac>] (__vfs_read)
[<c0231c5c>] (__vfs_read) from [<c0231ee0>] (vfs_read)
[<c0231e34>] (vfs_read) from [<c0232464>] (ksys_read)
[<c02323f0>] (ksys_read) from [<c02324fc>] (sys_read)
[<c02324e4>] (sys_read) from [<c00091d0>] (__sys_trace_return)

Signed-off-by: bumwoo lee <bw365.lee@...sung.com>
---
 drivers/extcon/extcon.c | 29 +++++++++++++++++------------
 1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/drivers/extcon/extcon.c b/drivers/extcon/extcon.c
index d27cd9f88f86..d3a32b806499 100644
--- a/drivers/extcon/extcon.c
+++ b/drivers/extcon/extcon.c
@@ -1224,19 +1224,14 @@ int extcon_dev_register(struct extcon_dev *edev)
 		edev->dev.type = &edev->extcon_dev_type;
 	}
 
-	ret = device_register(&edev->dev);
-	if (ret) {
-		put_device(&edev->dev);
-		goto err_dev;
-	}
-
 	spin_lock_init(&edev->lock);
-	edev->nh = devm_kcalloc(&edev->dev, edev->max_supported,
-				sizeof(*edev->nh), GFP_KERNEL);
-	if (!edev->nh) {
-		ret = -ENOMEM;
-		device_unregister(&edev->dev);
-		goto err_dev;
+	if (edev->max_supported) {
+		edev->nh = kcalloc(edev->max_supported, sizeof(*edev->nh),
+				GFP_KERNEL);
+		if (!edev->nh) {
+			ret = -ENOMEM;
+			goto err_alloc_nh;
+		}
 	}
 
 	for (index = 0; index < edev->max_supported; index++)
@@ -1247,6 +1242,12 @@ int extcon_dev_register(struct extcon_dev *edev)
 	dev_set_drvdata(&edev->dev, edev);
 	edev->state = 0;
 
+	ret = device_register(&edev->dev);
+	if (ret) {
+		put_device(&edev->dev);
+		goto err_dev;
+	}
+
 	mutex_lock(&extcon_dev_list_lock);
 	list_add(&edev->entry, &extcon_dev_list);
 	mutex_unlock(&extcon_dev_list_lock);
@@ -1254,6 +1255,9 @@ int extcon_dev_register(struct extcon_dev *edev)
 	return 0;
 
 err_dev:
+	if (edev->max_supported)
+		kfree(edev->nh);
+err_alloc_nh:
 	if (edev->max_supported)
 		kfree(edev->extcon_dev_type.groups);
 err_alloc_groups:
@@ -1314,6 +1318,7 @@ void extcon_dev_unregister(struct extcon_dev *edev)
 	if (edev->max_supported) {
 		kfree(edev->extcon_dev_type.groups);
 		kfree(edev->cables);
+		kfree(edev->nh);
 	}
 
 	put_device(&edev->dev);
-- 
2.35.1