Re: [PATCH] leds: fix a potential NULL pointer dereference

[Jacek Anaszewski]

Hi Geert,

On 4/1/19 9:08 AM, Geert Uytterhoeven wrote:
> Hi Jacek,
>
> On Sun, Mar 31, 2019 at 1:01 PM Jacek Anaszewski
> <jacek.anaszewski@xxxxxxxxx> wrote:
> > On 3/31/19 11:06 AM, Geert Uytterhoeven wrote:
> > On Sun, Mar 10, 2019 at 9:40 PM Jacek Anaszewski
> > > <jacek.anaszewski@xxxxxxxxx> wrote:
> > > > On 3/9/19 7:04 AM, Kangjie Lu wrote:
> > > > > In case of_match_device cannot find a match, the fixes returns
> > > > > -EINVAL to avoid NULL pointer dereference.
> > > > >
> > > > > Signed-off-by: Kangjie Lu <kjlu@xxxxxxx>
> > > > > ---
> > > > >     drivers/leds/leds-pca9532.c | 8 ++++++--
> > > > >     1 file changed, 6 insertions(+), 2 deletions(-)
> > > > >
> > > > > diff --git a/drivers/leds/leds-pca9532.c b/drivers/leds/leds-pca9532.c
> > > > > index 7fea18b0c15d..4b0335591728 100644
> > > > > --- a/drivers/leds/leds-pca9532.c
> > > > > +++ b/drivers/leds/leds-pca9532.c
> > > > > @@ -513,6 +513,7 @@ static int pca9532_probe(struct i2c_client *client,
> > > > >         const struct i2c_device_id *id)
> > > > >     {
> > > > >         int devid;
> > > > > +     const struct of_device_id *of_id;
> > > > >         struct pca9532_data *data = i2c_get_clientdata(client);
> > > > >         struct pca9532_platform_data *pca9532_pdata =
> > > > >                         dev_get_platdata(&client->dev);
> > > > > @@ -528,8 +529,11 @@ static int pca9532_probe(struct i2c_client *client,
> > > > >                         dev_err(&client->dev, "no platform data\n");
> > > > >                         return -EINVAL;
> > > > >                 }
> > > > > -             devid = (int)(uintptr_t)of_match_device(
> > > > > -                     of_pca9532_leds_match, &client->dev)->data;
> > > > > +             of_id = of_match_device(of_pca9532_leds_match,
> > > > > +                             &client->dev);
> > > > > +             if (unlikely(!of_id))
> > >
> > > Use of unlikey() is frowned upon.
> >
> > What do you mean? Can you give some reference?
>
> I have more memories of this being discussed, but I could find only
> https://lwn.net/Articles/420019/

Thanks!

> It may be useful for some heavily used core code, but not in most drivers
> or uncritical code like probe paths, due to:
>    - many people getting it wrong,
>    - usually it doesn't make any difference at all.
>
> > > > Applied to the for-5.2 branch of linux-leds.git.
> > >
> > > And also as a fix for v5.1...
> >
> > Yes, but it had been in linux-next for almost two weeks before that.
>
> Sorry, I only noticed when it got upstream.

No problem.

--
Best regards,
Jacek Anaszewski