Re: [PATCH 2/2] bus: mhi: ep: Add missing state_lock protection for mhi_state accesses

[Manivannan Sadhasivam]

On Tue, Feb 03, 2026 at 12:25:02PM +0530, Sumit Kumar wrote:
> The mhi_cntrl->mhi_state field should be protected by state_lock to
> ensure atomic state transitions. However, mhi_ep_handle_syserr() and
> mhi_ep_power_up() access mhi_state without holding this lock, which can
> race with concurrent state transitions and lead to state corruption.
> 
> Add proper state_lock protection in both functions around their mhi_state
> accesses.
> 
> Fixes: fb3a26b7e8af ("bus: mhi: ep: Add support for powering up the MHI endpoint stack")
> Fixes: f7d0806bdb1b3 ("bus: mhi: ep: Add support for handling SYS_ERR condition")
> Signed-off-by: Sumit Kumar <sumit.kumar@xxxxxxxxxxxxxxxx>
> ---
>  drivers/bus/mhi/ep/main.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/bus/mhi/ep/main.c b/drivers/bus/mhi/ep/main.c
> index 73597de373ef7e0c428bcbc126d63a9a97f95144..e9d14006453aa8b8999486a1cef17ca43f4cc4e1 100644
> --- a/drivers/bus/mhi/ep/main.c
> +++ b/drivers/bus/mhi/ep/main.c
> @@ -1113,7 +1113,9 @@ void mhi_ep_handle_syserr(struct mhi_ep_cntrl *mhi_cntrl)
>  	struct device *dev = &mhi_cntrl->mhi_dev->dev;
>  	int ret;
>  
> +	mutex_lock(&mhi_cntrl->state_lock);
>  	ret = mhi_ep_set_mhi_state(mhi_cntrl, MHI_STATE_SYS_ERR);
> +	mutex_unlock(&mhi_cntrl->state_lock);

Ah, I sent my patch *before* seeing this one. But still this part is wrong and
will cause deadlock as callers were already holding 'state_lock'.

So drop this part in favor of:
https://lore.kernel.org/mhi/20260302085612.18725-1-manivannan.sadhasivam@xxxxxxxxxxxxxxxx

>  	if (ret)
>  		return;
>  
> @@ -1148,7 +1150,9 @@ int mhi_ep_power_up(struct mhi_ep_cntrl *mhi_cntrl)
>  	for (i = 0; i < mhi_cntrl->event_rings; i++)
>  		mhi_ep_ring_init(&mhi_cntrl->mhi_event[i].ring, RING_TYPE_ER, i);
>  
> +	mutex_lock(&mhi_cntrl->state_lock);
>  	mhi_cntrl->mhi_state = MHI_STATE_RESET;
> +	mutex_unlock(&mhi_cntrl->state_lock);
>  

This looks fine.

- Mani

-- 
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