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Message-ID: <21b7da6c-1d93-c7a1-65b6-80a59d8c982e@free-electrons.com>
Date: Fri, 29 Sep 2017 14:37:47 +0200
From: Quentin Schulz <quentin.schulz@...e-electrons.com>
To: Julia Lawall <julia.lawall@...6.fr>
Cc: linus.walleij@...aro.org, robh+dt@...nel.org, mark.rutland@....com,
wens@...e.org, linux@...linux.org.uk,
maxime.ripard@...e-electrons.com, lee.jones@...aro.org,
linux-gpio@...r.kernel.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-sunxi@...glegroups.com, thomas.petazzoni@...e-electrons.com,
kbuild-all@...org
Subject: Re: [PATCH v2 02/10] pinctrl: axp209: add pinctrl features (fwd)
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.
2) The "new" gpio->functions would never be freed.
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@...el.com>
> To: kbuild@...org
> Cc: Julia Lawall <julia.lawall@...6.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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