linux-kernel - [PATCH] block: xen-blkback: add null check to avoid null pointer dereference

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Date:   Thu, 11 May 2017 10:27:35 -0500
From:   "Gustavo A. R. Silva" <garsilva@...eddedor.com>
To:     Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Roger Pau Monné <roger.pau@...rix.com>,
        Juergen Gross <jgross@...e.com>
Cc:     xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <garsilva@...eddedor.com>
Subject: [PATCH] block: xen-blkback: add null check to avoid null pointer
 dereference

Add null check before calling xen_blkif_put() to avoid potential
null pointer dereference.

Addresses-Coverity-ID: 1350942
Cc: Juergen Gross <jgross@...e.com>
Signed-off-by: Gustavo A. R. Silva <garsilva@...eddedor.com>
---
 drivers/block/xen-blkback/xenbus.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index 8fe61b5..1f3dfaa 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -504,11 +504,13 @@ static int xen_blkbk_remove(struct xenbus_device *dev)
 
 	dev_set_drvdata(&dev->dev, NULL);
 
-	if (be->blkif)
+	if (be->blkif) {
 		xen_blkif_disconnect(be->blkif);
 
-	/* Put the reference we set in xen_blkif_alloc(). */
-	xen_blkif_put(be->blkif);
+		/* Put the reference we set in xen_blkif_alloc(). */
+		xen_blkif_put(be->blkif);
+	}
+
 	kfree(be->mode);
 	kfree(be);
 	return 0;
-- 
2.5.0