block: Fix race during disk initialization
When a new disk is being discovered, add_disk() first ties the bdev to gendisk
(via register_disk()->blkdev_get()) and only after that calls
bdi_register_bdev(). Because register_disk() also creates disk's kobject, it
can happen that userspace manages to open and modify the device's data (or
inode) before its BDI is properly initialized leading to a warning in
__mark_inode_dirty().
Fix the problem by registering BDI early enough.
This patch addresses https://bugzilla.kernel.org/show_bug.cgi?id=16312
Cc: stable@kernel.org
Reported-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/block/genhd.c b/block/genhd.c
index 5c9c503..7923e72 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -541,13 +541,15 @@
disk->major = MAJOR(devt);
disk->first_minor = MINOR(devt);
+ /* Register BDI before referencing it from bdev */
+ bdi = &disk->queue->backing_dev_info;
+ bdi_register_dev(bdi, disk_devt(disk));
+
blk_register_region(disk_devt(disk), disk->minors, NULL,
exact_match, exact_lock, disk);
register_disk(disk);
blk_register_queue(disk);
- bdi = &disk->queue->backing_dev_info;
- bdi_register_dev(bdi, disk_devt(disk));
retval = sysfs_create_link(&disk_to_dev(disk)->kobj, &bdi->dev->kobj,
"bdi");
WARN_ON(retval);