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

[Mario Limonciello]

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@xxxxxxxxx>
> > Closes: https://lore.kernel.org/linux-usb/700df3c4-2f6c-85f9-6c61-065bc5b2db3a@xxxxxxxxx/
> > Suggested-by: Dave Hansen <dave.hansen@xxxxxxxxx>
> > Suggested-by: Mario Limonciello <mario.limonciello@xxxxxxx>
> > Cc: Saranya Gopal <saranya.gopal@xxxxxxxxx>
> > Signed-off-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>

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.

> thanks,
>
> greg k-h