linux-kernel - [PATCH] block: xen-blkfront: Fix possible NULL ptr dereference

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Date:	Sat,  9 Nov 2013 13:36:09 -0200
From:	Felipe Pena <felipensp@...il.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	David Vrabel <david.vrabel@...rix.com>
Cc:	xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
	Felipe Pena <felipensp@...il.com>
Subject: [PATCH] block: xen-blkfront: Fix possible NULL ptr dereference

In the blkif_release function the bdget_disk() call might returns
a NULL ptr which might be dereferenced on bdev->bd_openers checking

Signed-off-by: Felipe Pena <felipensp@...il.com>
---
 drivers/block/xen-blkfront.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index a4660bb..7bb1552 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -1959,6 +1959,9 @@ static void blkif_release(struct gendisk *disk, fmode_t mode)
 
 	bdev = bdget_disk(disk, 0);
 
+	if (!bdev)
+		goto out_mutex;
+
 	if (bdev->bd_openers)
 		goto out;
 
@@ -1989,6 +1992,7 @@ static void blkif_release(struct gendisk *disk, fmode_t mode)
 
 out:
 	bdput(bdev);
+out_mutex:
 	mutex_unlock(&blkfront_mutex);
 }
 
-- 
1.7.10.4

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