linux-kernel - [PATCH] drivers:block:mtip32xx:mtip32xx:change the order of null-pointer dereference validation

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Date:   Tue, 25 Apr 2017 18:30:16 -0700
From:   Heloise <os@...as.ac.cn>
To:     axboe@...com, hare@...e.com, jthumshirn@...e.de,
        keith.busch@...el.com, ming.lei@...hat.com, bianpan2016@....com,
        dan.j.williams@...el.com, sachin.s5@...sung.com,
        baoyou.xie@...aro.org
Cc:     linux-kernel@...r.kernel.org, Heloise <os@...as.ac.cn>
Subject: [PATCH] drivers:block:mtip32xx:mtip32xx:change the order of null-pointer dereference validation

Signed-off-by: Heloise <os@...as.ac.cn>

mtip_async_complete() uses the variable port 'port->dd'at the begining, then
validates null-pointer dereference of port 'unlikely(!port)'. Change the order
of validation.
---
 drivers/block/mtip32xx/mtip32xx.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/block/mtip32xx/mtip32xx.c b/drivers/block/mtip32xx/mtip32xx.c
index 1d1dc11..feed61a 100644
--- a/drivers/block/mtip32xx/mtip32xx.c
+++ b/drivers/block/mtip32xx/mtip32xx.c
@@ -228,10 +228,13 @@ static struct mtip_cmd *mtip_cmd_from_tag(struct driver_data *dd,
 static void mtip_async_complete(struct mtip_port *port,
 				int tag, struct mtip_cmd *cmd, int status)
 {
+	if (unlikely(!port))
+		return;
+
 	struct driver_data *dd = port->dd;
 	struct request *rq;
 
-	if (unlikely(!dd) || unlikely(!port))
+	if (unlikely(!dd))
 		return;
 
 	if (unlikely(status == PORT_IRQ_TF_ERR)) {
-- 
2.1.0