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From:   Lv Yunlong <lyl2019@mail.ustc.edu.cn>
To:     sathya.prakash@broadcom.com, sreekanth.reddy@broadcom.com,
        suganath-prabu.subramani@broadcom.com, jejb@linux.ibm.com,
        martin.petersen@oracle.com
Cc:     MPT-FusionLinux.pdl@broadcom.com, linux-scsi@vger.kernel.org,
        linux-kernel@vger.kernel.org, Lv Yunlong <lyl2019@mail.ustc.edu.cn>
Subject: [PATCH] scsi: fix a error refcount get in pcie_device_make_active
Date:   Mon, 22 Mar 2021 19:35:01 -0700
Message-Id: <20210323023501.11314-1-lyl2019@mail.ustc.edu.cn>
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In pcie_device_make_active, pcie_device may be freed by
pcie_device_put(pcie_device). After it, the refcount of
pcie_device is increased by pcie_device_get(pcie_device).
The pcie_device is freed but refcount is non-zero. It could
cause use after free later.

My patch puts the pcie_device_get() ahead of pcie_device_put()
to avoid uaf.

Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
---
 drivers/scsi/mpt3sas/mpt3sas_scsih.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/mpt3sas/mpt3sas_scsih.c b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
index ffca03064797..17061f54d616 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_scsih.c
+++ b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
@@ -11432,12 +11432,12 @@ static void pcie_device_make_active(struct MPT3SAS_ADAPTER *ioc,
 	unsigned long flags;
 
 	spin_lock_irqsave(&ioc->pcie_device_lock, flags);
-
+	pcie_device_get(pcie_device);
+
 	if (!list_empty(&pcie_device->list)) {
 		list_del_init(&pcie_device->list);
 		pcie_device_put(pcie_device);
 	}
-	pcie_device_get(pcie_device);
 	list_add_tail(&pcie_device->list, &ioc->pcie_device_list);
 
 	spin_unlock_irqrestore(&ioc->pcie_device_lock, flags);
-- 
2.25.1