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

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Message-Id: <20221215033132.230023-1-longman@redhat.com>
Date:   Wed, 14 Dec 2022 22:31:30 -0500
From:   Waiman Long <longman@...hat.com>
To:     Jens Axboe <axboe@...nel.dk>, Tejun Heo <tj@...nel.org>,
        Josef Bacik <josef@...icpanda.com>,
        Zefan Li <lizefan.x@...edance.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     cgroups@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Michal Koutný <mkoutny@...e.com>,
        "Dennis Zhou (Facebook)" <dennisszhou@...il.com>,
        Waiman Long <longman@...hat.com>
Subject: [PATCH v4 0/2] blk-cgroup: Fix potential UAF & flush rstat at blkgs destruction path

 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