linux-kernel - Re: [PATCH] power: sequencing: fix NULL-pointer dereference in error path

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Message-ID: <CAMRc=MdqZZLJLrAb10amgZSz40k1qAVMohVeUvHqobEHR5qaZw@mail.gmail.com>
Date: Fri, 12 Jul 2024 17:02:25 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: Krzysztof Kozlowski <krzk@...nel.org>, linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH] power: sequencing: fix NULL-pointer dereference in error path

On Fri, Jul 12, 2024 at 4:59 PM Dan Carpenter <dan.carpenter@...aro.org> wrote:
>
> On Fri, Jul 12, 2024 at 04:45:46PM +0200, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> >
> > We may call pwrseq_target_free() on a target without the final unit
> > assigned yet. In this case pwrseq_unit_put() will dereference
> > a NULL-pointer. Add a check to the latter function.
> >
> > Fixes: 249ebf3f65f8 ("power: sequencing: implement the pwrseq core")
> > Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
> > Closes: https://lore.kernel.org/linux-pm/62a3531e-9927-40f8-b587-254a2dfa47ef@stanley.mountain/
> > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> > ---
> >  drivers/power/sequencing/core.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/power/sequencing/core.c b/drivers/power/sequencing/core.c
> > index 9c32b07a55e7..fe07100e4b33 100644
> > --- a/drivers/power/sequencing/core.c
> > +++ b/drivers/power/sequencing/core.c
> > @@ -119,7 +119,8 @@ static void pwrseq_unit_release(struct kref *ref);
> >
> >  static void pwrseq_unit_put(struct pwrseq_unit *unit)
> >  {
> > -     kref_put(&unit->ref, pwrseq_unit_release);
> > +     if (unit)
>
> I was wondering where you would put the check.  But it needs to be:
>
>         if (!IS_ERR_OR_NULL(unit))
>
> regards,
> dan carpenter
>

Am I missing something? pwrseq_unit_new() can only return NULL on error.

Bart

> > +             kref_put(&unit->ref, pwrseq_unit_release);
> >  }
> >
> >  /**
> > --
> > 2.43.0