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Message-ID: <7cdfa93b-70f7-4912-bda7-a6b50b93c665@acm.org>
Date: Mon, 18 Dec 2023 13:41:35 -0800
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Subject: Re: [PATCH] scsi: ufs: core: Let the sq_lock protect sq_tail_slot
 access
Content-Language: en-US
To: Can Guo <quic_cang@quicinc.com>, mani@kernel.org,
 adrian.hunter@intel.com, beanhuo@micron.com, avri.altman@wdc.com,
 junwoo80.lee@samsung.com, martin.petersen@oracle.com
Cc: linux-scsi@vger.kernel.org, linux-arm-msm@vger.kernel.org,
 Alim Akhtar <alim.akhtar@samsung.com>,
 "James E.J. Bottomley" <jejb@linux.ibm.com>,
 Stanley Chu <stanley.chu@mediatek.com>,
 Asutosh Das <quic_asutoshd@quicinc.com>, Peter Wang
 <peter.wang@mediatek.com>, "Bao D. Nguyen" <quic_nguyenb@quicinc.com>,
 Arthur Simchaev <Arthur.Simchaev@wdc.com>,
 open list <linux-kernel@vger.kernel.org>
References: <1702913550-20631-1-git-send-email-quic_cang@quicinc.com>
From: Bart Van Assche <bvanassche@acm.org>
In-Reply-To: <1702913550-20631-1-git-send-email-quic_cang@quicinc.com>
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On 12/18/23 07:32, 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@quicinc.com>
> 
> 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-by: Bart Van Assche <bvanassche@acm.org>