Re: [PATCH v3] i2c: busses: i2c-pxa.c: Fix for possible null pointer dereferenc

[Emil Goode]

Hello,

I noticed one more thing.

On Fri, Jul 04, 2014 at 07:07:48PM +0200, Rickard Strandqvist wrote:
> 2014-07-04 11:10 GMT+02:00 Emil Goode <emilgoode@xxxxxxxxx>:
> > Hello Rickard,
> >
> > Since this is a probe function there is also no need to release the devm_*
> > resources in the i2c_pxa_remove function, this leads to double free.
> >
> > Also I have a few nit-pick comments below.
> >
> > On Thu, Jul 03, 2014 at 10:19:16PM +0200, Rickard Strandqvist wrote:
> >> Fix for possible null pointer dereferenc, and there is a risk for memory leak if something unexpected happens and the function returns.
> >> It now use Managed Device Resource instead.
> >>
> >> Signed-off-by: Rickard Strandqvist <rickard_strandqvist@xxxxxxxxxxxxxxxxxx>
> >> ---
> >>  drivers/i2c/busses/i2c-pxa.c |   37 ++++++++++++++++---------------------
> >>  1 file changed, 16 insertions(+), 21 deletions(-)
> >>
> >> diff --git a/drivers/i2c/busses/i2c-pxa.c b/drivers/i2c/busses/i2c-pxa.c
> >> index be671f7..2edb633 100644
> >> --- a/drivers/i2c/busses/i2c-pxa.c
> >> +++ b/drivers/i2c/busses/i2c-pxa.c
> >> @@ -1141,10 +1141,10 @@ static int i2c_pxa_probe(struct platform_device *dev)
> >>       struct resource *res = NULL;
> >>       int ret, irq;
> >>
> >> -     i2c = kzalloc(sizeof(struct pxa_i2c), GFP_KERNEL);
> >> +     i2c = devm_kzalloc(&dev->dev, sizeof(struct pxa_i2c), GFP_KERNEL);
> >>       if (!i2c) {
> >>               ret = -ENOMEM;
> >> -             goto emalloc;
> >> +             goto err_nothing_to_release;
> >
> > Perhaps its a good idea to return directly here, then the label
> > err_nothing_to_release can be removed.
> >
> >>       }
> >>
> >>       /* Default adapter num to device id; i2c_pxa_probe_dt can override. */
> >> @@ -1154,18 +1154,19 @@ static int i2c_pxa_probe(struct platform_device *dev)
> >>       if (ret > 0)
> >>               ret = i2c_pxa_probe_pdata(dev, i2c, &i2c_type);
> >>       if (ret < 0)
> >> -             goto eclk;
> >> +             goto err_nothing_to_release;
> >
> > Same here.
> >
> >>
> >>       res = platform_get_resource(dev, IORESOURCE_MEM, 0);
> >>       irq = platform_get_irq(dev, 0);
> >>       if (res == NULL || irq < 0) {
> >>               ret = -ENODEV;
> >> -             goto eclk;
> >> +             goto err_nothing_to_release;
> >
> > Same here.
> >
> >>       }
> >>
> >> -     if (!request_mem_region(res->start, resource_size(res), res->name)) {
> >> +     if (!devm_request_mem_region(&dev->dev, res->start,
> >> +                             resource_size(res), res->name)) {
> >>               ret = -ENOMEM;
> >> -             goto eclk;
> >> +             goto emalloc;
> >
> > We could also return directly here since the release_mem_region call should
> > be removed, as mentioned in Jingoos reply.
> >
> >>       }
> >>
> >>       i2c->adap.owner   = THIS_MODULE;
> >> @@ -1176,16 +1177,16 @@ static int i2c_pxa_probe(struct platform_device *dev)
> >>
> >>       strlcpy(i2c->adap.name, "pxa_i2c-i2c", sizeof(i2c->adap.name));
> >>
> >> -     i2c->clk = clk_get(&dev->dev, NULL);
> >> +     i2c->clk = devm_clk_get(&dev->dev, NULL);
> >>       if (IS_ERR(i2c->clk)) {
> >>               ret = PTR_ERR(i2c->clk);
> >> -             goto eclk;
> >> +             goto emalloc;
> >
> > Same here.
> >
> >>       }
> >>
> >> -     i2c->reg_base = ioremap(res->start, resource_size(res));
> >> -     if (!i2c->reg_base) {
> >> +     i2c->reg_base = devm_ioremap_resource(&adev->dev, res));
> >> +     if (IS_ERR(i2c->reg_base)) {
> >>               ret = -EIO;
> >> -             goto eremap;
> >> +             goto emalloc;
> >
> > Same here.
> >
> >>       }
> >>
> >>       i2c->reg_ibmr = i2c->reg_base + pxa_reg_layout[i2c_type].ibmr;
> >> @@ -1227,10 +1228,10 @@ static int i2c_pxa_probe(struct platform_device *dev)
> >>               i2c->adap.algo = &i2c_pxa_pio_algorithm;
> >>       } else {
> >>               i2c->adap.algo = &i2c_pxa_algorithm;
> >> -             ret = request_irq(irq, i2c_pxa_handler, IRQF_SHARED,
> >> -                               dev_name(&dev->dev), i2c);
> >> +             ret = devm_request_irq(&dev->dev, irq, i2c_pxa_handler,
> >> +                              IRQF_SHARED, dev_name(&dev->dev), i2c);
> >>               if (ret)
> >> -                     goto ereqirq;
> >> +                     goto emalloc;
> >
> > Same here.
> >
> >>       }
> >>
> >>       i2c_pxa_reset(i2c);
> >> @@ -1261,15 +1262,9 @@ static int i2c_pxa_probe(struct platform_device *dev)
> >>  eadapt:
> >>       if (!i2c->use_pio)
> >>               free_irq(irq, i2c);
> >
> > The free_irq() call should also be removed since devm_request_irq() was used.
> >
> >> -ereqirq:
> >> -     clk_disable_unprepare(i2c->clk);

I think we should keep the clk_disable_unprepare() call.

> >> -     iounmap(i2c->reg_base);
> >> -eremap:
> >> -     clk_put(i2c->clk);
> >> -eclk:
> >> -     kfree(i2c);
> >>  emalloc:
> >>       release_mem_region(res->start, resource_size(res));
> >> +err_nothing_to_release:
> >>       return ret;
> >>  }
> >>
> >
> > Best regards,
> >
> > Emil Goode
> 
> Hi All!
> 
> Ok, so there is literally nothing to do release anymore.
> A good system Devres, I understand you want everyone to use it.
> 
> I also think it is also better to return directly then.
> But who decides, Wolfram?

Yes, Wolfram is the maintainer.

Personally I would do the devm_* convertion in a second patch.

Best regards,

Emil Goode

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