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

[Bao D. Nguyen]

On 12/18/2023 7:32 AM, 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()")
> Signed-off-by: Can Guo <quic_cang@xxxxxxxxxxx>
>
> 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);

Reviewed and Tested-by: Bao D. Nguyen <quic_nguyenb@xxxxxxxxxxx>