4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Vasilis Liaskovitis <vliaskovitis@xxxxxxxx>
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@xxxxxxxxxxxxxxx # 4.5 and later
Signed-off-by: Vasilis Liaskovitis <vliaskovitis@xxxxxxxx>
Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/block/xen-blkfront.c | 3 +++
1 file changed, 3 insertions(+)
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -2524,6 +2524,9 @@ 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);
