linux-kernel - Re: [RFC PATCH] char: misc: Init misc->list in a safe way

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Message-ID: <CAK8P3a3H5E487CeaCzFRoEpzQfFePZK+z0nQ6HEDtWJN7t=NAA@mail.gmail.com>
Date:   Mon, 26 Jun 2017 12:02:48 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Orson Zhai <orson.zhai@...eadtrum.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Zhongping Tan <zhongping.tan@...eadtrum.com>
Subject: Re: [RFC PATCH] char: misc: Init misc->list in a safe way

On Mon, Jun 26, 2017 at 11:31 AM, Orson Zhai <orson.zhai@...eadtrum.com> wrote:
> From: Zhongping Tan <zhongping.tan@...eadtrum.com>
>
> It is likely to enter a wrong case and return an error when registerring
> a misc device. As a result, misc->list will be intialized to a dead loop
> which is possible to go into wrong situation if anyone refers to it else
> where.
>
> Move the initializion line out of all error branches to avoid any side
> effect.
>
> Signed-off-by: Zhongping Tan <zhongping.tan@...eadtrum.com>
> Signed-off-by: Orson Zhai <orson.zhai@...eadtrum.com>

I fail to see the problem. Did you run into a bug that gets fixed by
this patch, or did you arrive here after code inspection?

As far as I can tell, the INIT_LIST_HEAD() on the entry has
no effect at all, the fields simply get initialized in the list_add(),
and the list traversal is protected using misc_mtx.

       Arnd