linux-kernel - RE: [PATCH v2] rpmsg: char: Avoid double destroy of default endpoint

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Date:   Wed, 21 Sep 2022 08:18:45 +0000
From:   Peng Fan <peng.fan@....com>
To:     "S.J. Wang" <shengjiu.wang@....com>,
        "andersson@...nel.org" <andersson@...nel.org>,
        "mathieu.poirier@...aro.org" <mathieu.poirier@...aro.org>,
        "arnaud.pouliquen@...s.st.com" <arnaud.pouliquen@...s.st.com>
CC:     "linux-remoteproc@...r.kernel.org" <linux-remoteproc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "shengjiu.wang@...il.com" <shengjiu.wang@...il.com>
Subject: RE: [PATCH v2] rpmsg: char: Avoid double destroy of default endpoint

> Subject: [PATCH v2] rpmsg: char: Avoid double destroy of default endpoint
> 
> 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
> 
> The issue can be reproduced by stopping remoteproc before closing the
> /dev/rpmsgX.
> 
> Fixes: bea9b79c2d10 ("rpmsg: char: Add possibility to use default endpoint
> of the rpmsg device")
> Signed-off-by: Shengjiu Wang <shengjiu.wang@....com>
> Reviewed-by: Arnaud Pouliquen <arnaud.pouliquen@...s.st.com>
> ---
> changes in v2:
> - Add comments
> 
>  drivers/rpmsg/rpmsg_char.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c
> index 0850ae34fb88..3e0b8f3496ed 100644
> --- a/drivers/rpmsg/rpmsg_char.c
> +++ b/drivers/rpmsg/rpmsg_char.c
> @@ -76,7 +76,9 @@ int rpmsg_chrdev_eptdev_destroy(struct device *dev,
> void *data)
> 
>  	mutex_lock(&eptdev->ept_lock);
>  	if (eptdev->ept) {
> -		rpmsg_destroy_ept(eptdev->ept);
> +		/* The default endpoint is released by the rpmsg core */
> +		if (!eptdev->default_ept)
> +			rpmsg_destroy_ept(eptdev->ept);
>  		eptdev->ept = NULL;
>  	}
>  	mutex_unlock(&eptdev->ept_lock);
> --

Reviewed-by: Peng Fan <peng.fan@....com>