linux-kernel - [PATCH] scsi: aacraid: fix a potential data inconsistency caused by double-fetch

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Message-Id: <20181225211136.69702-1-kjlu@umn.edu>
Date:   Tue, 25 Dec 2018 15:11:36 -0600
From:   Kangjie Lu <kjlu@....edu>
To:     kjlu@....edu
Cc:     pakki001@....edu,
        Adaptec OEM Raid Solutions <aacraid@...rosemi.com>,
        "James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] scsi: aacraid: fix a potential data inconsistency caused by double-fetch

"user_srb->count" may be changed by malicious user races. Let's set
"user_srbcmd->count" fetched in the second copy to be the one fetched in
the first copy.

Signed-off-by: Kangjie Lu <kjlu@....edu>
---
 drivers/scsi/aacraid/commctrl.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/scsi/aacraid/commctrl.c b/drivers/scsi/aacraid/commctrl.c
index 25f6600d6c09..eb18117c431a 100644
--- a/drivers/scsi/aacraid/commctrl.c
+++ b/drivers/scsi/aacraid/commctrl.c
@@ -539,6 +539,8 @@ static int aac_send_raw_srb(struct aac_dev* dev, void __user * arg)
 		rcode = -EFAULT;
 		goto cleanup;
 	}
+	/* Ensure user_srb->count is not changed */
+	user_srbcmd->count = fibsize;
 
 	flags = user_srbcmd->flags; /* from user in cpu order */
 	switch (flags & (SRB_DataIn | SRB_DataOut)) {
-- 
2.17.2 (Apple Git-113)