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Date: Mon, 12 Dec 2022 17:16:38 -0500
From: Waiman Long <longman@...hat.com>
To: Tejun Heo <tj@...nel.org>
Cc: Jens Axboe <axboe@...nel.dk>, Josef Bacik <josef@...icpanda.com>,
Zefan Li <lizefan.x@...edance.com>,
Johannes Weiner <hannes@...xchg.org>,
Andrew Morton <akpm@...ux-foundation.org>,
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>,
Yi Zhang <yi.zhang@...hat.com>
Subject: Re: [PATCH-block v2 1/3] bdi, blk-cgroup: Fix potential UAF of blkcg
On 12/12/22 17:13, Tejun Heo wrote:
> On Sun, Dec 11, 2022 at 05:20:56PM -0500, Waiman Long wrote:
>> static void blkcg_destroy_blkgs(struct blkcg *blkcg)
>> {
>> + /*
>> + * blkcg_destroy_blkgs() shouldn't be called with all the blkcg
>> + * references gone.
>> + */
>> + if (WARN_ON_ONCE(!css_tryget(&blkcg->css)))
>> + return;
> Wouldn't it make more sense to use percpu_ref_is_zero()? It's not like the
> obtained extra reference does anything, right?
Yes, that makes sense. Will incorporate the change in the next version.
Thanks,
Longman
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