From: Cathy Avery <cathy.avery@oracle.com>
Date: Fri, 23 Oct 2015 10:12:46 +0000 (+0800)
Subject: xen-blkfront: check for null drvdata in blkback_changed (XenbusStateClosing)
X-Git-Tag: v4.1.12-92~247^2~1
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=bc9a10ed433fec684cee2332e9045f13aab6f36f;p=users%2Fjedix%2Flinux-maple.git

xen-blkfront: check for null drvdata in blkback_changed (XenbusStateClosing)

Orabug: 21935345

xen-blkfront will crash if the check to talk_to_blkback()
in blkback_changed()(XenbusStateInitWait) returns an error.
The driver data is freed and info is set to NULL. Later during
the close process via talk_to_blkback's call to xenbus_dev_fatal()
the null pointer is passed to and dereference in blkfront_closing.

Signed-off-by: Cathy Avery <cathy.avery@oracle.com>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Joe Jin <joe.jin@oracle.com>
---

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 7a8a73f1fc04..d68b08ae4be1 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -1984,7 +1984,8 @@ static void blkback_changed(struct xenbus_device *dev,
 			break;
 		/* Missed the backend's Closing state -- fallthrough */
 	case XenbusStateClosing:
-		blkfront_closing(info);
+		if (info)
+			blkfront_closing(info);
 		break;
 	}
 }