• Tejun Heo's avatar
    block: fix disk->part[] dereferencing race · e71bf0d0
    Tejun Heo authored
    disk->part[] is protected by its matching bdev's lock.  However,
    non-critical accesses like collecting stats and printing out sysfs and
    proc information used to be performed without any locking.  As
    partitions can come and go dynamically, partitions can go away
    underneath those non-critical accesses.  As some of those accesses are
    writes, this theoretically can lead to silent corruption.
    This patch fixes the race by using RCU for the partition array and dev
    reference counter to hold partitions.
    * Rename disk->part[] to disk->__part[] to make sure no one outside
      genhd layer proper accesses it directly.
    * Use RCU for disk->__part[] dereferencing.
    * Implement disk_{get|put}_part() which can be used to get and put
      partitions from gendisk respectively.
    * Iterators are implemented to help iterate through all partitions
    * Functions which require RCU readlock are marked with _rcu suffix.
    * Use disk_put_part() in __blkdev_put() instead of directly putting
      the contained kobject.
    Signed-off-by: default avatarTejun Heo <tj@kernel.org>
    Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
blk-merge.c 9.77 KB