4.18-stable review patch. If anyone has any objections, please let me know.
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From: Vasilis Liaskovitis vliaskovitis@suse.com
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: stable@vger.kernel.org # 4.5 and later Signed-off-by: Vasilis Liaskovitis vliaskovitis@suse.com Reviewed-by: Roger Pau Monné roger.pau@citrix.com Signed-off-by: Konrad Rzeszutek Wilk konrad.wilk@oracle.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/block/xen-blkfront.c | 3 +++ 1 file changed, 3 insertions(+)
--- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -2475,6 +2475,9 @@ 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);