[Xen-devel] [PATCH] xen-blkfront: check for null drvdata in blkback_changed (XenbusStateClosing)

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

From: Cathy Avery <cathy.avery@xxxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 drivers/block/xen-blkfront.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 0823a96..04fc7b4 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -1955,7 +1955,8 @@ 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;
        }
 }
-- 
2.4.3


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