[PATCH v4 0/2] blk-cgroup: Fix potential UAF & flush rstat at blkgs destruction path

From: Waiman Long <longman@redhat.com>
To: Jens Axboe <axboe@kernel.dk>, Tejun Heo <tj@kernel.org>,
	Josef Bacik <josef@toxicpanda.com>,
	Zefan Li <lizefan.x@bytedance.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Andrew Morton <akpm@linux-foundation.org>
Cc: cgroups@vger.kernel.org, linux-block@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	"Michal Koutný" <mkoutny@suse.com>,
	"Dennis Zhou (Facebook)" <dennisszhou@gmail.com>,
	"Waiman Long" <longman@redhat.com>
Subject: [PATCH v4 0/2] blk-cgroup: Fix potential UAF & flush rstat at blkgs destruction path
Date: Wed, 14 Dec 2022 22:31:30 -0500	[thread overview]
Message-ID: <20221215033132.230023-1-longman@redhat.com> (raw)

 v4:
  - Update comment and commit logs for both patches.

 v3:
  - Drop v2 patch 2 as it may not be needed.
  - Replace css_tryget() with percpu_ref_is_zero() in patch 1 as
    suggested by Tejun.
  - Expand comment on patch 2 to elaborate the reason for this patch.

 v2:
  - Remove unnecessary rcu_read_{lock|unlock} from
    cgroup_rstat_css_cpu_flush() in patch 3.

It was found that blkcg_destroy_blkgs() may be called with all blkcg
references gone. This may potentially cause user-after-free and so should
be fixed. The second patch flushes rstat when calling blkcg_destroy_blkgs().

Waiman Long (2):
  bdi, blk-cgroup: Fix potential UAF of blkcg
  blk-cgroup: Flush stats at blkgs destruction path

 block/blk-cgroup.c     | 23 +++++++++++++++++++++++
 include/linux/cgroup.h |  1 +
 kernel/cgroup/rstat.c  | 18 ++++++++++++++++++
 mm/backing-dev.c       |  8 ++++++--
 4 files changed, 48 insertions(+), 2 deletions(-)

-- 
2.31.1