linux-kernel - Re: [PATCH v2 2/2] i2c: dev: don't allow user-space to deadlock the kernel

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Message-ID: <CAMRc=MfEt50RE3KWE5_4g509bbUgZcCrtEFvikskuKYaGLQU0w@mail.gmail.com>
Date:   Wed, 18 Jan 2023 16:07:11 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Hillf Danton <hdanton@...a.com>
Cc:     Wolfram Sang <wsa@...nel.org>, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v2 2/2] i2c: dev: don't allow user-space to deadlock the kernel

On Wed, Jan 18, 2023 at 3:59 PM Hillf Danton <hdanton@...a.com> wrote:
>
> On Thu, 29 Dec 2022 17:00:45 +0100 Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> >
> > @@ -44,8 +45,14 @@ struct i2c_dev {
> >       struct i2c_adapter *adap;
> >       struct device dev;
> >       struct cdev cdev;
> > +     struct rw_semaphore sem;
>
>         int                     state;
> #define STATE_RELEASED 1
> #define STATE_DETACHED 2
> >  };
>
> Because syscalls like read, write and ioctl have completed upon release,
> serializing the release and detach pathes is a cure to the issue.
>

Please elaborate because I have no idea what you mean by that.

Bart