[BUG] block: bdi_register_owner() failure cause NULL pointer dereference
From: Michael Wang <hidden>
Date: 2016-09-29 13:03:43
Also in:
lkml
Subsystem:
block layer, the rest · Maintainers:
Jens Axboe, Linus Torvalds
Hi, Folks We observed the hard lockup while trying raid assemble with sas3ircu, it was start with the failure inside bdi_register_owner() with duplicated kobj path, and later comeup the NULL pointer dereference, after that system hang and we saw hard lockup on screen. The duplicated issue could be with the scsi controller driver and we are going to upgrade it anyway, but my question is why we don't do some error handling like:
diff --git a/block/genhd.c b/block/genhd.c
index a178c8e..318bc63 100644
--- a/block/genhd.c
+++ b/block/genhd.c@@ -614,7 +614,15 @@ void device_add_disk(struct device *parent, struct gendisk *disk) /* Register BDI before referencing it from bdev */ bdi = &disk->queue->backing_dev_info; - bdi_register_owner(bdi, disk_to_dev(disk)); + if (bdi_register_owner(bdi, disk_to_dev(disk))) { + disk_release_events(disk); + blk_free_devt(devt); + disk->ev = NULL; + disk->first_minor = 0; + disk->major = 0; + WARN_ON(1); + return; + } blk_register_region(disk_devt(disk), disk->minors, NULL, exact_match, exact_lock, disk);
to prevent the following NULL pointer dereference and hard lockup? Regards, Michael Wang