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

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Date:   Tue, 12 Sep 2023 23:00:51 +0800
From:   Chen Yu <yu.c.chen@...el.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
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

Hi Greg,

thanks for your time,

On 2023-09-11 at 20:59:18 +0200, Greg Kroah-Hartman wrote:
> 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 :(
>

Ah, the 'Commit' was incorrectly added.

> > 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 for this link, I'll patch my kernel using above version.

thanks,
Chenyu