On Thu, Oct 11, 2018 at 06:20:00PM +0200, Vasilis Liaskovitis wrote: > 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. > > Signed-off-by: Vasilis Liaskovitis <vliaskovitis@xxxxxxxx> > --- > drivers/block/xen-blkfront.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c > index 429d20131c7e..92cc6cb6b078 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) > + goto out; I don't see the point in adding the 'out' label. Can you just return 0 here? Thanks, Roger.
