blk-cgroup: fix list corruption from reorder of WRITE ->lqueued

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: blk-cgroup: fix list corruption from reorder of WRITE ->lqueued __blkcg_rstat_flush() can be run anytime, especially when blk_cgroup_bio_start is being executed. If WRITE of `->lqueued` is re-ordered with READ of 'bisc->lnode.next' in the loop of __blkcg_rstat_flush(), `next_bisc` can be assigned with one stat instance being added in blk_cgroup_bio_start(), then the local list in __blkcg_rstat_flush() could be corrupted. Fix the issue by adding one barrier.

References

• https://git.kernel.org/stable/c/714e59b5456e4d6e4295a9968c564abe193f461c
• https://git.kernel.org/stable/c/785298ab6b802afa75089239266b6bbea590809c
• https://git.kernel.org/stable/c/d0aac2363549e12cc79b8e285f13d5a9f42fd08e