linux-kernel - [patch 2/2] mvsas: dereferencing before checking

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Message-ID: <20100811074157.GB30429@bicker>
Date:	Wed, 11 Aug 2010 09:41:57 +0200
From:	Dan Carpenter <error27@...il.com>
To:	"James E.J. Bottomley" <James.Bottomley@...e.de>
Cc:	Jiri Slaby <jslaby@...e.cz>, Srinivas <satyasrinivasp@....in>,
	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: [patch 2/2] mvsas: dereferencing before checking

If "mvi_dev" is NULL then we have to test it at the start of the function
and return if it is null.  In the original code, we dereferenced "mvi_dev"
before the check to assign "mvi" and then we dereferenced "mvi" to take
the spin lock.

Signed-off-by: Dan Carpenter <error27@...il.com>

diff --git a/drivers/scsi/mvsas/mv_sas.c b/drivers/scsi/mvsas/mv_sas.c
index 406246c..a5c5aa5 100644
--- a/drivers/scsi/mvsas/mv_sas.c
+++ b/drivers/scsi/mvsas/mv_sas.c
@@ -1379,19 +1379,21 @@ void mvs_dev_gone_notify(struct domain_device *dev)
 {
 	unsigned long flags = 0;
 	struct mvs_device *mvi_dev = dev->lldd_dev;
-	struct mvs_info *mvi = mvi_dev->mvi_info;
-
-	spin_lock_irqsave(&mvi->lock, flags);
+	struct mvs_info *mvi;
 
-	if (mvi_dev) {
-		mv_dprintk("found dev[%d:%x] is gone.\n",
-			mvi_dev->device_id, mvi_dev->dev_type);
-		mvs_release_task(mvi, dev);
-		mvs_free_reg_set(mvi, mvi_dev);
-		mvs_free_dev(mvi_dev);
-	} else {
+	if (!mvi_dev) {
 		mv_dprintk("found dev has gone.\n");
+		return;
 	}
+
+	mvi = mvi_dev->mvi_info;
+	spin_lock_irqsave(&mvi->lock, flags);
+
+	mv_dprintk("found dev[%d:%x] is gone.\n",
+		mvi_dev->device_id, mvi_dev->dev_type);
+	mvs_release_task(mvi, dev);
+	mvs_free_reg_set(mvi, mvi_dev);
+	mvs_free_dev(mvi_dev);
 	dev->lldd_dev = NULL;
 
 	spin_unlock_irqrestore(&mvi->lock, flags);
--
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