Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:5 as permitted sender) client-ip=2620:137:e000::3:5;
MIME-Version: 1.0
References: <ZQs1RgTKg6VJqmPs@google.com>
In-Reply-To: <ZQs1RgTKg6VJqmPs@google.com>
From:   Linus Walleij <linus.walleij@linaro.org>
Date:   Mon, 25 Sep 2023 15:30:53 +0200
Message-ID: <CACRpkdbuOn4gKBE-tB4MHQ3mx_ujQZLdPp1hp75ANFgsGb1jQQ@mail.gmail.com>
Subject: Re: [PATCH] pinctrl: avoid unsafe code pattern in find_pinctrl()
To:     Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc:     Bartosz Golaszewski <bartosz.golaszewski@linaro.org>,
        linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Wed, Sep 20, 2023 at 8:09=E2=80=AFPM Dmitry Torokhov
<dmitry.torokhov@gmail.com> wrote:

> The code in find_pinctrl() takes a mutex and traverses a list of pinctrl
> structures. Later the caller bumps up reference count on the found
> structure. Such pattern is not safe as pinctrl that was found may get
> deleted before the caller gets around to increasing the reference count.
>
> Fix this by taking the reference count in find_pinctrl(), while it still
> holds the mutex.
>
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

After some thinking, applied for fixes and tagged for stable as
it is a very real problem that can cause random crashes under
the right circumstances.

Thanks for finding this Dmitry!!

Yours,
Linus Walleij