Re: [PATCH] scsi: ufs: core: Let the sq_lock protect sq_tail_slot access

[Manivannan Sadhasivam <mani@kernel.org>]

On Mon, Dec 18, 2023 at 07:32:17AM -0800, Can Guo wrote:
> If access sq_tail_slot without the protection from the sq_lock, race
> condition can have multiple SQEs copied to duplicate SQE slot(s), which can
> lead to multiple incredible stability issues. Fix it by moving the *dest
> initialization, in ufshcd_send_command(), back under protection from the
> sq_lock.
> 
> Fixes: 3c85f087faec ("scsi: ufs: mcq: Use pointer arithmetic in ufshcd_send_command()")

Cc: stable@vger.kernel.org

> Signed-off-by: Can Guo <quic_cang@quicinc.com>

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

- Mani

> 
> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> index ae9936f..2994aac 100644
> --- a/drivers/ufs/core/ufshcd.c
> +++ b/drivers/ufs/core/ufshcd.c
> @@ -2274,9 +2274,10 @@ void ufshcd_send_command(struct ufs_hba *hba, unsigned int task_tag,
>  	if (is_mcq_enabled(hba)) {
>  		int utrd_size = sizeof(struct utp_transfer_req_desc);
>  		struct utp_transfer_req_desc *src = lrbp->utr_descriptor_ptr;
> -		struct utp_transfer_req_desc *dest = hwq->sqe_base_addr + hwq->sq_tail_slot;
> +		struct utp_transfer_req_desc *dest;
>  
>  		spin_lock(&hwq->sq_lock);
> +		dest = hwq->sqe_base_addr + hwq->sq_tail_slot;
>  		memcpy(dest, src, utrd_size);
>  		ufshcd_inc_sq_tail(hwq);
>  		spin_unlock(&hwq->sq_lock);
> -- 
> 2.7.4
> 

-- 
மணிவண்ணன் சதாசிவம்