linux-kernel - [PATCH] usb: typec: ucsi: Release debugfs only if it has been allocated

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Message-Id: <20230911162706.2856910-1-yu.c.chen@intel.com>
Date:   Tue, 12 Sep 2023 00:27:06 +0800
From:   Chen Yu <yu.c.chen@...el.com>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Saranya Gopal <saranya.gopal@...el.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Chen Yu <yu.c.chen@...el.com>
Subject: [PATCH] usb: typec: ucsi: Release debugfs only if it has been allocated

The following NULL pointer exception was found during boot up:

 calling  ucsi_acpi_platform_driver_init+0x0/0xff0 [ucsi_acpi] @ 394
 initcall mac_hid_init+0x0/0xff0 [mac_hid] returned 0 after 5 usecs
 BUG: kernel NULL pointer dereference, address: 0000000000000020
 Call Trace:
  ? ucsi_debugfs_unregister+0x15/0x30 [typec_ucsi]
  ucsi_destroy+0x17/0x30 [typec_ucsi]
  ucsi_acpi_probe+0x1d5/0x230 [ucsi_acpi]

It is possible that ucsi_acpi_probe() fails to install the notifier,
and calls ucsi_destroy() to release the resource. However at that
moment the debugfs has not been registered yet, thus the NULL pointer
exception is triggered. Add the check for debugfs pointer.

Fixes: Commit df0383ffad64 ("usb: typec: ucsi: Add debugfs for ucsi commands")
Signed-off-by: Chen Yu <yu.c.chen@...el.com>
---
 drivers/usb/typec/ucsi/debugfs.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/typec/ucsi/debugfs.c b/drivers/usb/typec/ucsi/debugfs.c
index 0c7bf88d4a7f..55533dc3d539 100644
--- a/drivers/usb/typec/ucsi/debugfs.c
+++ b/drivers/usb/typec/ucsi/debugfs.c
@@ -84,7 +84,8 @@ void ucsi_debugfs_register(struct ucsi *ucsi)

 void ucsi_debugfs_unregister(struct ucsi *ucsi)
 {
-	debugfs_remove_recursive(ucsi->debugfs->dentry);
+	if (ucsi->debugfs)
+		debugfs_remove_recursive(ucsi->debugfs->dentry);
 	kfree(ucsi->debugfs);
 }

-- 
2.25.1