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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Yihang Li <liyihang6@hisilicon.com>,
        John Garry <john.garry@huawei.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.18 505/879] scsi: hisi_sas: Fix memory ordering in hisi_sas_task_deliver()
Date:   Tue,  7 Jun 2022 19:00:23 +0200
Message-Id: <20220607165017.534549158@linuxfoundation.org>
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From: John Garry <john.garry@huawei.com>

[ Upstream commit 6c6ac8b7773f05f93dc4e4044686e059d1f78dea ]

The memories for the slot should be observed to be written prior to
observing the slot as ready.

Prior to commit 26fc0ea74fcb ("scsi: libsas: Drop SAS_TASK_AT_INITIATOR"),
we had a spin_lock() + spin_unlock() immediately before marking the slot as
ready. The spin_unlock() - with release semantics - caused the slot memory
to be observed to be written.

Now that the spin_lock() + spin_unlock() is gone, use a smp_wmb().

Link: https://lore.kernel.org/r/1652774661-12935-1-git-send-email-john.garry@huawei.com
Fixes: 26fc0ea74fcb ("scsi: libsas: Drop SAS_TASK_AT_INITIATOR")
Reported-by: Yihang Li <liyihang6@hisilicon.com>
Tested-by: Yihang Li <liyihang6@hisilicon.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/scsi/hisi_sas/hisi_sas_main.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/scsi/hisi_sas/hisi_sas_main.c b/drivers/scsi/hisi_sas/hisi_sas_main.c
index 86cbfab78dfe..849cc5fc86af 100644
--- a/drivers/scsi/hisi_sas/hisi_sas_main.c
+++ b/drivers/scsi/hisi_sas/hisi_sas_main.c
@@ -446,6 +446,8 @@ void hisi_sas_task_deliver(struct hisi_hba *hisi_hba,
 		return;
 	}
 
+	/* Make slot memories observable before marking as ready */
+	smp_wmb();
 	WRITE_ONCE(slot->ready, 1);
 
 	spin_lock(&dq->lock);
-- 
2.35.1