linux-kernel - Re: [PATCH] rpmsg: char: Avoid double destroy of default endpoint

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Date:   Mon, 19 Sep 2022 14:50:30 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Shengjiu Wang <shengjiu.wang@....com>, arnaud.pouliquen@...s.st.com
Cc:     linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org,
        shengjiu.wang@...il.com, Bjorn Andersson <andersson@...nel.org>
Subject: Re: [PATCH] rpmsg: char: Avoid double destroy of default endpoint

On Fri, 16 Sept 2022 at 00:57, Shengjiu Wang <shengjiu.wang@....com> wrote:
>
> The rpmsg_dev_remove() in rpmsg_core is the place for releasing
> this default endpoint.
>
> So need to avoid destroying the default endpoint in
> rpmsg_chrdev_eptdev_destroy(), this should be the same as
> rpmsg_eptdev_release(). Otherwise there will be double destroy
> issue that ept->refcount report warning:
>
> refcount_t: underflow; use-after-free.
>
> Call trace:
>  refcount_warn_saturate+0xf8/0x150
>  virtio_rpmsg_destroy_ept+0xd4/0xec
>  rpmsg_dev_remove+0x60/0x70
>
> Fixes: bea9b79c2d10 ("rpmsg: char: Add possibility to use default endpoint of the rpmsg device")
> Signed-off-by: Shengjiu Wang <shengjiu.wang@....com>
> ---
>  drivers/rpmsg/rpmsg_char.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c
> index 0850ae34fb88..562d545ac0d3 100644
> --- a/drivers/rpmsg/rpmsg_char.c
> +++ b/drivers/rpmsg/rpmsg_char.c
> @@ -76,7 +76,8 @@ int rpmsg_chrdev_eptdev_destroy(struct device *dev, void *data)
>
>         mutex_lock(&eptdev->ept_lock);
>         if (eptdev->ept) {
> -               rpmsg_destroy_ept(eptdev->ept);
> +               if (!eptdev->default_ept)
> +                       rpmsg_destroy_ept(eptdev->ept);
>                 eptdev->ept = NULL;

Arnaud - please look into this one.

Thanks,
Mathieu

>         }
>         mutex_unlock(&eptdev->ept_lock);
> --
> 2.34.1
>