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

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Date:   Wed, 1 Feb 2023 22:26:46 -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>
Subject: Re: [PATCH v4 0/2] blk-cgroup: Fix potential UAF & flush rstat at
 blkgs destruction path


On 12/14/22 22:31, Waiman Long wrote:
>   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(-)
>
Ping!

Any comments on these patches.

Thanks,
Longman