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

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Message-ID: <2023091140-getting-seldom-1046@gregkh>
Date:   Mon, 11 Sep 2023 13:52:56 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Thorsten Leemhuis <regressions@...mhuis.info>
Cc:     Mario Limonciello <mario.limonciello@....com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.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,
        Linux kernel regressions list <regressions@...ts.linux.dev>
Subject: Re: [PATCH] usb: typec: ucsi: Fix NULL pointer dereference

On Mon, Sep 11, 2023 at 11:46:17AM +0200, Thorsten Leemhuis wrote:
> On 06.09.23 14:05, Mario Limonciello wrote:
> > On 9/6/2023 03:57, Greg Kroah-Hartman wrote:
> >> 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>
> > 
> > I could also reproduce it with 7733171926cc336ddf0c8f847eefaff569dbff86
> > on two different laptops.
> > 
> >>> ---
> >>>   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.
> > 
> > It might be worth sending before rc1 if it ends up being widespread.
> 
> FWIW, as someone that afaics just ran into the regression fixed by this
> patch with -rc1, I would have liked that patch to be in -rc1 as well...

It's now queued up and will go to Linus this week.

thanks,

greg k-h