linux-kernel - Re: BUG: drivers/pinctrl/core: races in pinctrl

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Date:   Thu, 14 Jun 2018 14:12:14 +0200
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Discussions about the Letux Kernel 
        <letux-kernel@...nphoenux.org>, kernel@...a-handheld.com
Subject: Re: BUG: drivers/pinctrl/core: races in pinctrl_groups and deferred probing

Hi Tony,

> Am 14.06.2018 um 14:01 schrieb Tony Lindgren <tony@...mide.com>:
> 
> * H. Nikolaus Schaller <hns@...delico.com> [180613 12:41]:
>> 
>> Now if I look into pinctrl_generic_add_group() and pinctrl_generic_get_group_name(),
>> pctldev->num_groups++ is not protected if pinctrl_generic_add_group() may be called by
>> two threads in parallel for the same pctldev. Hence a second thread may try to insert
>> a different node into the radix tree at the same selector index. This fails but there
>> is no error check - and the second entry is completely missing (but probably assumed to
>> be there).
> 
> Sounds like pinctrl-single.c is missing mutex around calls to
> pinctrl_generic_add_group()?

Yes, that could be. I didn't research the call path, just the one of
devm_pinctrl_get(). That uses a mutex in

https://elixir.bootlin.com/linux/v4.17.1/source/drivers/pinctrl/core.c#L1021

Maybe a similar mutex is missing elsewhere.

BR,
Nikolaus