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    Subject[PATCH 3.13.y-ckt 67/96] xen-blkfront: check for null drvdata in blkback_changed (XenbusStateClosing)
    Date
    3.13.11-ckt30 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Cathy Avery <cathy.avery@oracle.com>

    commit a54c8f0f2d7df525ff997e2afe71866a1a013064 upstream.

    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>
    Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    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 fdee753..0035645e 100644
    --- a/drivers/block/xen-blkfront.c
    +++ b/drivers/block/xen-blkfront.c
    @@ -1917,7 +1917,8 @@ 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;
    }
    }
    --
    1.9.1


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