Re: [PATCH v2] remoteproc: Add a new remoteproc state RPROC_DEFUNCT

[Mukesh Ojha]

On Tue, Oct 15, 2024 at 02:01:18AM +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().
> 
> There is other side to this issue if we want to fix this via adding a
> NULL check on glink->edge which does not guarantees that the remoteproc
> will recover in second call from Process B as it has failed in the first
> Process A during SMC shutdown call and may again fail at the same call
> and rproc can not recover for such case.
> 
> Add a new rproc state RPROC_DEFUNCT i.e., non recoverable state of
> remoteproc and the only way to recover from it via system restart.
> 
> 	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
>      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@xxxxxxxxxxx>
> ---
> Changes in v2:
>  - Removed NULL pointer check instead added a new state to signify
>    non-recoverable state of remoteproc.
> 
>  drivers/remoteproc/remoteproc_core.c  | 3 ++-
>  drivers/remoteproc/remoteproc_sysfs.c | 1 +
>  include/linux/remoteproc.h            | 5 ++++-
>  3 files changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
> index f276956f2c5c..494c8fcc63ca 100644
> --- a/drivers/remoteproc/remoteproc_core.c
> +++ b/drivers/remoteproc/remoteproc_core.c
> @@ -1727,6 +1727,7 @@ static int rproc_stop(struct rproc *rproc, bool crashed)
>  	/* power off the remote processor */
>  	ret = rproc->ops->stop(rproc);
>  	if (ret) {
> +		rproc->state = RPROC_DEFUNCT;

I have put it here, but I am more inclined towards adding this
assignment in qcom remoteproc(pas) driver.

-Mukesh

>  	}
> @@ -1839,7 +1840,7 @@ int rproc_trigger_recovery(struct rproc *rproc)
>  		return ret;
>  
>  	/* State could have changed before we got the mutex */
> -	if (rproc->state != RPROC_CRASHED)
> +	if (rproc_start == RPROC_DEFUNCT || rproc->state != RPROC_CRASHED)
>  		goto unlock_mutex;
>  
>  	dev_err(dev, "recovering %s\n", rproc->name);
> diff --git a/drivers/remoteproc/remoteproc_sysfs.c b/drivers/remoteproc/remoteproc_sysfs.c
> index 138e752c5e4e..5f722b4576b2 100644
> --- a/drivers/remoteproc/remoteproc_sysfs.c
> +++ b/drivers/remoteproc/remoteproc_sysfs.c
> @@ -171,6 +171,7 @@ static const char * const rproc_state_string[] = {
>  	[RPROC_DELETED]		= "deleted",
>  	[RPROC_ATTACHED]	= "attached",
>  	[RPROC_DETACHED]	= "detached",
> +	[RPROC_DEFUNCT]		= "defunct",
>  	[RPROC_LAST]		= "invalid",
>  };
>  
> diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
> index b4795698d8c2..3e4ba06c6a9a 100644
> --- a/include/linux/remoteproc.h
> +++ b/include/linux/remoteproc.h
> @@ -417,6 +417,8 @@ struct rproc_ops {
>   *			has attached to it
>   * @RPROC_DETACHED:	device has been booted by another entity and waiting
>   *			for the core to attach to it
> + * @RPROC_DEFUNCT:	device neither crashed nor responding to any of the
> + * 			requests and can only recover on system restart.
>   * @RPROC_LAST:		just keep this one at the end
>   *
>   * Please note that the values of these states are used as indices
> @@ -433,7 +435,8 @@ enum rproc_state {
>  	RPROC_DELETED	= 4,
>  	RPROC_ATTACHED	= 5,
>  	RPROC_DETACHED	= 6,
> -	RPROC_LAST	= 7,
> +	RPROC_DEFUNCT	= 7,
> +	RPROC_LAST	= 8,
>  };
>  
>  /**
> -- 
> 2.34.1
>