linux-kernel - Re: [PATCH] mhi_bus: core: Check state before processing power

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Date:   Wed, 17 Feb 2021 09:00:26 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Jeffrey Hugo <jhugo@...eaurora.org>
Cc:     hemantk@...eaurora.org, bbhatt@...eaurora.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mhi_bus: core: Check state before processing power_down

On Tue, Feb 16, 2021 at 02:38:16PM -0700, Jeffrey Hugo wrote:
> We cannot process a power_down if the power state is DISABLED.  There is
> no valid mhi_ctxt in that case, so attepting to process the power_down
> will likely result in a null pointer dereference.  If the power state is
> DISABLED, there is nothing to do anyways, so just bail early.
> 
> Signed-off-by: Jeffrey Hugo <jhugo@...eaurora.org>
> ---
>  drivers/bus/mhi/core/pm.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/bus/mhi/core/pm.c b/drivers/bus/mhi/core/pm.c
> index 56ba3ab..dc69074 100644
> --- a/drivers/bus/mhi/core/pm.c
> +++ b/drivers/bus/mhi/core/pm.c
> @@ -1144,6 +1144,7 @@ int mhi_async_power_up(struct mhi_controller *mhi_cntrl)
>  		mhi_deinit_dev_ctxt(mhi_cntrl);
>  
>  error_dev_ctxt:
> +	mhi_cntrl->pm_state = MHI_PM_DISABLE;
>  	mutex_unlock(&mhi_cntrl->pm_mutex);

pm_lock is supposed to protect the PM state. The current code needs a cleanup
interms of locking. It's been on my TODO list for sometime...

>  
>  	return ret;
> @@ -1155,6 +1156,12 @@ void mhi_power_down(struct mhi_controller *mhi_cntrl, bool graceful)
>  	enum mhi_pm_state cur_state, transition_state;
>  	struct device *dev = &mhi_cntrl->mhi_dev->dev;
>  
> +	mutex_lock(&mhi_cntrl->pm_mutex);
> +	cur_state = mhi_cntrl->pm_state;
> +	mutex_unlock(&mhi_cntrl->pm_mutex);

Same here.

Thanks,
Mani

> +	if (cur_state == MHI_PM_DISABLE)
> +		return; /* Already powered down */
> +
>  	/* If it's not a graceful shutdown, force MHI to linkdown state */
>  	transition_state = (graceful) ? MHI_PM_SHUTDOWN_PROCESS :
>  			   MHI_PM_LD_ERR_FATAL_DETECT;
> -- 
> Qualcomm Technologies, Inc. is a member of the
> Code Aurora Forum, a Linux Foundation Collaborative Project.
>