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

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Message-ID: <bf3f5a67-f6cf-44ed-a2d8-5722dcae9869@suswa.mountain>
Date: Fri, 12 Jul 2024 10:24:11 -0500
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Bartosz Golaszewski <brgl@...ev.pl>
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 05:02:25PM +0200, Bartosz Golaszewski wrote:
> 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.
> 

It's not pwrseq_unit_new() but pwrseq_unit_setup() that's the issue.
The target->unit = pwrseq_unit_setup() assignment in
pwrseq_do_setup_targets().

regards,
dan carpenter