linux-kernel - Re: [PATCH v3 12/12] bus: mhi: core: Remove MHI event ring IRQ handlers when powering down

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Date:   Fri, 30 Oct 2020 19:41:46 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Bhaumik Bhatt <bbhatt@...eaurora.org>
Cc:     linux-arm-msm@...r.kernel.org, hemantk@...eaurora.org,
        jhugo@...eaurora.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 12/12] bus: mhi: core: Remove MHI event ring IRQ
 handlers when powering down

On Thu, Oct 29, 2020 at 09:10:57PM -0700, Bhaumik Bhatt wrote:
> While powering down, the device may or may not acknowledge an MHI
> RESET issued by host for a graceful shutdown scenario and end up
> sending an incoming data packet after tasklets have been killed.
> If a rogue device sends this interrupt for a data transfer event
> ring update, it can result in a tasklet getting scheduled while a
> clean up is ongoing or has completed and cause access to freed
> memory leading to a NULL pointer exception. Remove the interrupt
> handlers for MHI event rings early on to avoid this scenario.
> 
> Signed-off-by: Bhaumik Bhatt <bbhatt@...eaurora.org>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>

Thanks,
Mani

> ---
>  drivers/bus/mhi/core/pm.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/bus/mhi/core/pm.c b/drivers/bus/mhi/core/pm.c
> index ffbf6f5..a671f58 100644
> --- a/drivers/bus/mhi/core/pm.c
> +++ b/drivers/bus/mhi/core/pm.c
> @@ -494,6 +494,7 @@ static void mhi_pm_disable_transition(struct mhi_controller *mhi_cntrl)
>  	for (i = 0; i < mhi_cntrl->total_ev_rings; i++, mhi_event++) {
>  		if (mhi_event->offload_ev)
>  			continue;
> +		free_irq(mhi_cntrl->irq[mhi_event->irq], mhi_event);
>  		tasklet_kill(&mhi_event->task);
>  	}
>  
> @@ -1164,7 +1165,7 @@ void mhi_power_down(struct mhi_controller *mhi_cntrl, bool graceful)
>  	/* Wait for shutdown to complete */
>  	flush_work(&mhi_cntrl->st_worker);
>  
> -	mhi_deinit_free_irq(mhi_cntrl);
> +	free_irq(mhi_cntrl->irq[0], mhi_cntrl);
>  
>  	if (!mhi_cntrl->pre_init) {
>  		/* Free all allocated resources */
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>