Re: [PATCH 3/3] remoteproc: pru: Fix and cleanup firmware interrupt mapping logic

[Mathieu Poirier <mathieu.poirier@linaro.org>]

On Tue, Mar 23, 2021 at 05:38:39PM -0500, Suman Anna wrote:
> The PRU firmware interrupt mappings are configured and unconfigured in
> .start() and .stop() callbacks respectively using the variables 'evt_count'
> and a 'mapped_irq' pointer. These variables are modified only during these
> callbacks but are not re-initialized/reset properly during unwind or
> failure paths. These stale values caused a kernel crash while stopping a
> PRU remoteproc running a different firmware with no events on a subsequent
> run after a previous run that was running a firmware with events.
> 
> Fix this crash by ensuring that the evt_count is 0 and the mapped_irq
> pointer is set to NULL in pru_dispose_irq_mapping(). Also, reset these
> variables properly during any failures in the .start() callback. While
> at this, the pru_dispose_irq_mapping() callsites are all made to look
> the same, moving any conditional logic to inside the function.
> 
> Fixes: c75c9fdac66e ("remoteproc: pru: Add support for PRU specific interrupt configuration")
> Reported-by: Vignesh Raghavendra <vigneshr@ti.com>
> Signed-off-by: Suman Anna <s-anna@ti.com>
> ---
>  drivers/remoteproc/pru_rproc.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/remoteproc/pru_rproc.c b/drivers/remoteproc/pru_rproc.c
> index 87b43976c51b..5df19acb90ed 100644
> --- a/drivers/remoteproc/pru_rproc.c
> +++ b/drivers/remoteproc/pru_rproc.c
> @@ -266,12 +266,17 @@ static void pru_rproc_create_debug_entries(struct rproc *rproc)
>  
>  static void pru_dispose_irq_mapping(struct pru_rproc *pru)
>  {
> -	while (pru->evt_count--) {
> +	if (!pru->mapped_irq)
> +		return;
> +
> +	while (pru->evt_count) {
> +		pru->evt_count--;
>  		if (pru->mapped_irq[pru->evt_count] > 0)
>  			irq_dispose_mapping(pru->mapped_irq[pru->evt_count]);
>  	}
>  
>  	kfree(pru->mapped_irq);
> +	pru->mapped_irq = NULL;
>  }
>  
>  /*
> @@ -324,6 +329,8 @@ static int pru_handle_intrmap(struct rproc *rproc)
>  	of_node_put(parent);
>  	if (!irq_parent) {
>  		kfree(pru->mapped_irq);
> +		pru->mapped_irq = NULL;
> +		pru->evt_count = 0;

Patch 1/3 introduced a check on @parent that doesn't free pru->mapped_irq.  I
would also expect that error path to do the same has what is done here.  And
looking further up I see the error path for !pru->mapped_irq doesn't set
pru->evt_count to zero.

Thanks,
Mathieu

>  		return -ENODEV;
>  	}
>  
> @@ -398,8 +405,7 @@ static int pru_rproc_stop(struct rproc *rproc)
>  	pru_control_write_reg(pru, PRU_CTRL_CTRL, val);
>  
>  	/* dispose irq mapping - new firmware can provide new mapping */
> -	if (pru->mapped_irq)
> -		pru_dispose_irq_mapping(pru);
> +	pru_dispose_irq_mapping(pru);
>  
>  	return 0;
>  }
> -- 
> 2.30.1
>