linux-kernel - Re: pm_runtime_resume_and

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAJZ5v0h4qQoo5uVBLtSFhdVBpD1tpd-SmVzV1dE0+VZMrr-eTA@mail.gmail.com>
Date:   Wed, 13 Jul 2022 19:47:39 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: pm_runtime_resume_and_get in .remove callbacks

On Wed, Jul 13, 2022 at 10:47 AM Uwe Kleine-König
<u.kleine-koenig@...gutronix.de> wrote:
>
> Hello,
>
> there is a big bunch of kernel drivers (here:
> drivers/i2c/busses/i2c-sprd.c) that have a remove callback that looks as
> follows:
>
>         static int sprd_i2c_remove(struct platform_device *pdev)
>         {
>                 struct sprd_i2c *i2c_dev = platform_get_drvdata(pdev);
>                 int ret;
>
>                 ret = pm_runtime_resume_and_get(i2c_dev->dev);
>                 if (ret < 0)
>                         return ret;
>
>                 i2c_del_adapter(&i2c_dev->adap);
>                 clk_disable_unprepare(i2c_dev->clk);
>
>                 pm_runtime_put_noidle(i2c_dev->dev);
>                 pm_runtime_disable(i2c_dev->dev);
>
>                 return 0;
>         }
>
> If pm_runtime_resume_and_get fails, the i2c adapter isn't removed, but
> as the memory backing i2c_dev goes away---it was allocated using
> devm_kzalloc in .probe()---the next i2c action will probably access
> freed memory.
>
> I'm not familiar enough with pm-runtime stuff, but wonder what
> can/should be done about that. The obvious (to me) candidates are:
>
>  - log an error if pm_runtime_resume_and_get() fails, but continue to
>    clean up
>  - don't check the return value at all
>
> What do you think?

(1) Use pm_runtime_get_sync() instead of pm_runtime_resume_and_get()
and don't check its return value,

or if that is not viable, because something really can run if and only
if the device is operational,

(2) do something like

ret = pm_runtime_resume_and_get(i2c_dev->dev);
i2c_del_adapter(&i2c_dev->adap);
if (ret >= 0)
        clk_disable_unprepare(i2c_dev->clk);

pm_runtime_put_noidle(i2c_dev->dev);
pm_runtime_disable(i2c_dev->dev);

Thanks!