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SubjectRe: [PATCH v2 02/10] pinctrl: axp209: add pinctrl features (fwd)


On Fri, 29 Sep 2017, Quentin Schulz wrote:

> Hi Julia,
>
> On 29/09/2017 14:15, Julia Lawall wrote:
> > I'm not sure that it is allowed to do krealloc on devm allocated data.
> > See lins 468 and 485.
> >
>
> Indeed, from a glance at the code, it does not look like it is a good idea.
>
> For v3, this piece of code will be deleted anyway so it won't be a
> problem anymore.
>
> However, this logic is used in drivers/pinctrl/sunxi/pinctrl-sunxi.c[1][2]
>
> @Maxime, @Chen-Yu:
> We should check more thoroughly than what I did but I think Julia is right.
>
> The following is my understanding from a very quick look at the code.
>
> devm_kzalloc will register gpio->functions as a res of the device.
>
> However it's possible that the pointer is different after krealloc. In
> that case, krealloc will free the "old" gpio->functions[3] which is
> managed by devres.
>
> 1) We might be exposed to a free of a NULL pointer when devres takes
> care of unregistering the device.

I guess it would be a double free? krealloc won't update the devres view
of the pointer.

> 2) The "new" gpio->functions would never be freed.

That too.

julia

>
> Is that correct? If so, we should get rid of devm_kzalloc in favor of a
> simple kzalloc and free the pointer in the remove function of the driver.
>
> [1]
> http://elixir.free-electrons.com/linux/latest/source/drivers/pinctrl/sunxi/pinctrl-sunxi.c#L1078
> [2]
> http://elixir.free-electrons.com/linux/latest/source/drivers/pinctrl/sunxi/pinctrl-sunxi.c#L1107
> [3]
> http://elixir.free-electrons.com/linux/latest/source/mm/slab_common.c#L1414
>
> Thanks,
> Quentin
>
> > julia
> >
> > ---------- Forwarded message ----------
> > Date: Fri, 29 Sep 2017 20:00:03 +0800
> > From: kbuild test robot <fengguang.wu@intel.com>
> > To: kbuild@01.org
> > Cc: Julia Lawall <julia.lawall@lip6.fr>
> > Subject: Re: [PATCH v2 02/10] pinctrl: axp209: add pinctrl features
> >
> > Hi Quentin,
> >
> > [auto build test WARNING on ]
> >
> > url: https://github.com/0day-ci/linux/commits/Quentin-Schulz/add-pinmuxing-support-for-pins-in-AXP209-and-AXP813-PMICs/20170929-162846
> > base:
> > :::::: branch date: 4 hours ago
> > :::::: commit date: 4 hours ago
> >
> >>> drivers/pinctrl/pinctrl-axp209.c:485:19-27: WARNING: invalid free of devm_ allocated data
> >
> > # https://github.com/0day-ci/linux/commit/1e016076fb841f90f047d2b001c9f8d9fd5e2953
> > git remote add linux-review https://github.com/0day-ci/linux
> > git remote update linux-review
> > git checkout 1e016076fb841f90f047d2b001c9f8d9fd5e2953
> > vim +485 drivers/pinctrl/pinctrl-axp209.c
> >
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 446
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 447 static int axp20x_build_state(struct platform_device *pdev)
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 448 {
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 449 struct axp20x_gpio *gpio = platform_get_drvdata(pdev);
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 450 unsigned int npins = gpio->desc->npins;
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 451 const struct axp20x_desc_pin *pin;
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 452 struct axp20x_desc_function *func;
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 453 int i, ret;
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 454
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 455 gpio->ngroups = npins;
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 456 gpio->groups = devm_kzalloc(&pdev->dev,
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 457 gpio->ngroups * sizeof(*gpio->groups),
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 458 GFP_KERNEL);
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 459 if (!gpio->groups)
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 460 return -ENOMEM;
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 461
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 462 for (i = 0; i < npins; i++) {
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 463 gpio->groups[i].name = gpio->desc->pins[i].pin.name;
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 464 gpio->groups[i].pin = gpio->desc->pins[i].pin.number;
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 465 }
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 466
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 467 /* We assume 4 functions per pin should be enough as a default max */
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 468 gpio->functions = devm_kzalloc(&pdev->dev,
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 469 npins * 4 * sizeof(*gpio->functions),
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 470 GFP_KERNEL);
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 471 if (!gpio->functions)
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 472 return -ENOMEM;
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 473
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 474 /* Create a list of uniquely named functions */
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 475 for (i = 0; i < npins; i++) {
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 476 pin = &gpio->desc->pins[i];
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 477 func = pin->functions;
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 478
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 479 while (func->name) {
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 480 axp20x_pinctrl_add_function(gpio, func->name);
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 481 func++;
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 482 }
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 483 }
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 484
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 @485 gpio->functions = krealloc(gpio->functions,
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 486 gpio->nfunctions * sizeof(*gpio->functions),
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 487 GFP_KERNEL);
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 488
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 489 for (i = 0; i < npins; i++) {
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 490 pin = &gpio->desc->pins[i];
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 491 ret = axp20x_attach_group_function(pdev, pin);
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 492 if (ret)
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 493 return ret;
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 494 }
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 495
> > 1e016076fb drivers/pinctrl/pinctrl-axp209.c Quentin Schulz 2017-09-26 496 return 0;
> > f72f4b44df drivers/gpio/gpio-axp209.c Maxime Ripard 2016-07-20 497 }
> > f72f4b44df drivers/gpio/gpio-axp209.c Maxime Ripard 2016-07-20 498
> >
> > ---
> > 0-DAY kernel test infrastructure Open Source Technology Center
> > https://lists.01.org/pipermail/kbuild-all Intel Corporation
> >
>
> --
> Quentin Schulz, Free Electrons
> Embedded Linux and Kernel engineering
> http://free-electrons.com
>

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