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

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Message-ID: <20180615065810.GI112168@atomide.com>
Date:   Thu, 14 Jun 2018 23:58:10 -0700
From:   Tony Lindgren <tony@...mide.com>
To:     "H. Nikolaus Schaller" <hns@...delico.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

* H. Nikolaus Schaller <hns@...delico.com> [180614 12:15]:
> 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

In addition to missing mutex lock around the generic pinctrl functions
we also have racy helpers pinctrl_generic_remove_last_group() and
pinmux_generic_remove_last_function() like you pointed out. I'll post
a patch for you later on today to test.

Regards,

Tony