linux-kernel - Re: [PATCH] rpmsg: Avoid double-free in mtk_rpmsg_register

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Message-ID: <CANMq1KBJTpnYG59B1V=y_emqD3dtMZQAPY9bWJOC8FW2fNRgsA@mail.gmail.com>
Date:   Wed, 2 Sep 2020 19:04:27 +0800
From:   Nicolas Boichat <drinkcat@...omium.org>
To:     Markus Elfring <Markus.Elfring@....de>
Cc:     linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        "open list:REMOTE PROCESSOR (REMOTEPROC) SUBSYSTEM" 
        <linux-remoteproc@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        kernel-janitors@...r.kernel.org,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Ohad Ben-Cohen <ohad@...ery.com>,
        Pi-Hsun Shih <pihsun@...omium.org>
Subject: Re: [PATCH] rpmsg: Avoid double-free in mtk_rpmsg_register_device()

On Wed, Sep 2, 2020 at 5:33 PM Markus Elfring <Markus.Elfring@....de> wrote:
>
> > If rpmsg_register_device fails, it will call
> > mtk_rpmsg_release_device which already frees mdev.
>
> Can another imperative wording become helpful for the change description?
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?id=9c7d619be5a002ea29c172df5e3c1227c22cbb41#n151

Looking at your posting history, I'll leave it up to the maintainer.

> …
> > +++ b/drivers/rpmsg/mtk_rpmsg.c
> > @@ -220,10 +220,8 @@  static int mtk_rpmsg_register_device(struct mtk_rpmsg_rproc_subdev *mtk_subdev,
> >       rpdev->dev.release = mtk_rpmsg_release_device;
> >
> >       ret = rpmsg_register_device(rpdev);
> > -     if (ret) {
> > -             kfree(mdev);
> > +     if (ret)
> >               return ret;
> > -     }
> >
> >       return 0;
> >  }
>
>
> * How do you think about to use the following code variant instead?
>
>         return rpmsg_register_device(rpdev);
>
> * Would you like to omit the variable “ret” for this function implementation?

That's a good suggestion, I'll update and send a v2.

>
> Regards,
> Markus