From f92898e7f32e3533bfd95be174044bc349d416ca Mon Sep 17 00:00:00 2001 From: Vasilis Liaskovitis Date: Mon, 15 Oct 2018 15:25:08 +0200 Subject: xen/blkfront: avoid NULL blkfront_info dereference on device removal MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit If a block device is hot-added when we are out of grants, gnttab_grant_foreign_access fails with -ENOSPC (log message "28 granting access to ring page") in this code path: talk_to_blkback -> setup_blkring -> xenbus_grant_ring -> gnttab_grant_foreign_access and the failing path in talk_to_blkback sets the driver_data to NULL: destroy_blkring: blkif_free(info, 0); mutex_lock(&blkfront_mutex); free_info(info); mutex_unlock(&blkfront_mutex); dev_set_drvdata(&dev->dev, NULL); This results in a NULL pointer BUG when blkfront_remove and blkif_free try to access the failing device's NULL struct blkfront_info. Cc: stable@vger.kernel.org # 4.5 and later Signed-off-by: Vasilis Liaskovitis Reviewed-by: Roger Pau Monné Signed-off-by: Konrad Rzeszutek Wilk Signed-off-by: Jens Axboe --- drivers/block/xen-blkfront.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'drivers/block') diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c index 9eea83ae01c6..56452cabce5b 100644 --- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -2493,6 +2493,9 @@ static int blkfront_remove(struct xenbus_device *xbdev) dev_dbg(&xbdev->dev, "%s removed", xbdev->nodename); + if (!info) + return 0; + blkif_free(info, 0); mutex_lock(&info->mutex); -- cgit v1.2.3-59-g8ed1b