4.14-stable review patch. If anyone has any objections, please let me know.
------------------ From: Vasilis Liaskovitis <[email protected]> commit f92898e7f32e3533bfd95be174044bc349d416ca upstream. 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: [email protected] # 4.5 and later Signed-off-by: Vasilis Liaskovitis <[email protected]> Reviewed-by: Roger Pau Monné <[email protected]> Signed-off-by: Konrad Rzeszutek Wilk <[email protected]> Signed-off-by: Jens Axboe <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- drivers/block/xen-blkfront.c | 3 +++ 1 file changed, 3 insertions(+) --- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -2471,6 +2471,9 @@ static int blkfront_remove(struct xenbus dev_dbg(&xbdev->dev, "%s removed", xbdev->nodename); + if (!info) + return 0; + blkif_free(info, 0); mutex_lock(&info->mutex);
