linux-kernel - Re: [PATCH] remoteproc: qcom: Fix NULL pointer in glink_subdev

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Message-ID: <ZvTYA1Rg6DrEEabk@hu-bjorande-lv.qualcomm.com>
Date: Wed, 25 Sep 2024 20:41:55 -0700
From: Bjorn Andersson <quic_bjorande@...cinc.com>
To: Mukesh Ojha <quic_mojha@...cinc.com>
CC: Bjorn Andersson <andersson@...nel.org>,
        Mathieu Poirier
	<mathieu.poirier@...aro.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-remoteproc@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] remoteproc: qcom: Fix NULL pointer in glink_subdev_stop()

On Wed, Sep 25, 2024 at 04:03:51PM +0530, Mukesh Ojha wrote:
> Multiple call to glink_subdev_stop() for the same remoteproc can happen
> if rproc_stop() fails from Process-A that leaves the rproc state to
> RPROC_CRASHED state later a call to recovery_store from user space in
> Process B triggers rproc_trigger_recovery() of the same remoteproc to
> recover it results in NULL pointer dereference issue in
> qcom_glink_smem_unregister().
> 
> Fix it by having a NULL check in glink_subdev_stop().
> 
> 	Process-A                			Process-B
> 
>   fatal error interrupt happens
> 
>   rproc_crash_handler_work()
>     mutex_lock_interruptible(&rproc->lock);
>     ...
> 
>        rproc->state = RPROC_CRASHED;
>     ...
>     mutex_unlock(&rproc->lock);
> 
>     rproc_trigger_recovery()
>      mutex_lock_interruptible(&rproc->lock);
> 
>       adsp_stop()
>       qcom_q6v5_pas 20c00000.remoteproc: failed to shutdown: -22
>       remoteproc remoteproc3: can't stop rproc: -22

I presume that at this point this remoteproc is in some undefined state
and the only way to recover is for the user to reboot the machine?


The check for glink->edge avoids one pitfall following this, but I'd
prefer to see a solution that avoids issues in this scenario in the
remoteproc core - rather than working around side effects of this in
different places.

Regards,
Bjorn

>      mutex_unlock(&rproc->lock);
> 
> 						echo enabled > /sys/class/remoteproc/remoteprocX/recovery
> 						recovery_store()
> 						 rproc_trigger_recovery()
> 						  mutex_lock_interruptible(&rproc->lock);
> 						   rproc_stop()
> 						    glink_subdev_stop()
> 						      qcom_glink_smem_unregister() ==|
>                                                                                      |
>                                                                                      V
> 						      Unable to handle kernel NULL pointer dereference
>                                                                 at virtual address 0000000000000358
> 
> Signed-off-by: Mukesh Ojha <quic_mojha@...cinc.com>
> ---
> - We can do this NULL check in qcom_glink_smem_unregister() as it is
>   exported function however, there is only one user of this. So, doing
>   it with current approach should also be fine.
> 
>  drivers/remoteproc/qcom_common.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/remoteproc/qcom_common.c b/drivers/remoteproc/qcom_common.c
> index 8c8688f99f0a..52d6c9b99fdb 100644
> --- a/drivers/remoteproc/qcom_common.c
> +++ b/drivers/remoteproc/qcom_common.c
> @@ -209,6 +209,9 @@ static void glink_subdev_stop(struct rproc_subdev *subdev, bool crashed)
>  {
>  	struct qcom_rproc_glink *glink = to_glink_subdev(subdev);
>  
> +	if (!glink->edge)
> +		return;
> +
>  	qcom_glink_smem_unregister(glink->edge);
>  	glink->edge = NULL;
>  }
> -- 
> 2.34.1
> 
>