linux-kernel - Re: [PATCH] usb: typec: ucsi: Fix NULL pointer dereference

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Message-ID: <2023090638-overexert-endearing-3726@gregkh>
Date:   Wed, 6 Sep 2023 09:57:07 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc:     Mario Limonciello <mario.limonciello@....com>,
        Dave Hansen <dave.hansen@...el.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Saranya Gopal <saranya.gopal@...el.com>,
        Rajaram Regupathy <rajaram.regupathy@...el.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, Wayne Chang <waynec@...dia.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        linux-usb@...r.kernel.org
Subject: Re: [PATCH] usb: typec: ucsi: Fix NULL pointer dereference

On Wed, Sep 06, 2023 at 11:48:42AM +0300, Heikki Krogerus wrote:
> Making sure the UCSI debugfs entry actually exists before
> attempting to remove it.
> 
> Fixes: df0383ffad64 ("usb: typec: ucsi: Add debugfs for ucsi commands")
> Reported-by: Dave Hansen <dave.hansen@...el.com>
> Closes: https://lore.kernel.org/linux-usb/700df3c4-2f6c-85f9-6c61-065bc5b2db3a@intel.com/
> Suggested-by: Dave Hansen <dave.hansen@...el.com>
> Suggested-by: Mario Limonciello <mario.limonciello@....com>
> Cc: Saranya Gopal <saranya.gopal@...el.com>
> Signed-off-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> ---
>  drivers/usb/typec/ucsi/debugfs.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/usb/typec/ucsi/debugfs.c b/drivers/usb/typec/ucsi/debugfs.c
> index 0c7bf88d4a7f..f67733cecfdf 100644
> --- a/drivers/usb/typec/ucsi/debugfs.c
> +++ b/drivers/usb/typec/ucsi/debugfs.c
> @@ -84,6 +84,9 @@ void ucsi_debugfs_register(struct ucsi *ucsi)
>  
>  void ucsi_debugfs_unregister(struct ucsi *ucsi)
>  {
> +	if (IS_ERR_OR_NULL(ucsi) || !ucsi->debugfs)
> +		return;
> +
>  	debugfs_remove_recursive(ucsi->debugfs->dentry);

Why are you saving the dentry at all?  Why not just have debugfs look it
up when you want to remove it based on the filename?

Anyway, not a big deal here, just a comment.  I'll queue this up after
-rc1 is out.

thanks,

greg k-h