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[173.230.104.22]) by smtp.gmail.com with ESMTPSA id 196sm11399324itu.33.2018.12.25.12.24.53 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Tue, 25 Dec 2018 12:24:54 -0800 (PST) From: Kangjie Lu To: kjlu@umn.edu Cc: pakki001@umn.edu, Doug Gilbert , "James E.J. Bottomley" , "Martin K. Petersen" , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] scsi: fix a double-fetch bug in sg_write Date: Tue, 25 Dec 2018 14:24:26 -0600 Message-Id: <20181225202427.69476-1-kjlu@umn.edu> X-Mailer: git-send-email 2.17.2 (Apple Git-113) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org "opcode" has been copied in from user space and checked. We should not copy it in again, which may have been modified by malicous multi-threading user programs through race conditions. The fix uses the opcode fetched in the first copy. Signed-off-by: Kangjie Lu --- drivers/scsi/sg.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c index 4dacbfffd113..41774e4f9508 100644 --- a/drivers/scsi/sg.c +++ b/drivers/scsi/sg.c @@ -686,7 +686,8 @@ sg_write(struct file *filp, const char __user *buf, size_t count, loff_t * ppos) hp->flags = input_size; /* structure abuse ... */ hp->pack_id = old_hdr.pack_id; hp->usr_ptr = NULL; - if (__copy_from_user(cmnd, buf, cmd_size)) + cmnd[0] = opcode; + if (__copy_from_user(cmnd + 1, buf + 1, cmd_size - 1)) return -EFAULT; /* * SG_DXFER_TO_FROM_DEV is functionally equivalent to SG_DXFER_FROM_DEV, -- 2.17.2 (Apple Git-113)