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

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Date:   Mon, 11 Sep 2023 20:59:18 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Chen Yu <yu.c.chen@...el.com>
Cc:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Saranya Gopal <saranya.gopal@...el.com>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: typec: ucsi: Release debugfs only if it has been
 allocated

On Tue, Sep 12, 2023 at 12:27:06AM +0800, Chen Yu wrote:
> 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")

Incorrect format :(

> 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);
>  }

What's wrong with this patch instead:
	https://lore.kernel.org/all/20230906084842.1922052-1-heikki.krogerus@linux.intel.com/

thanks,

greg k-h