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References: <20230921182012.3965572-1-saranyamohan@google.com> <2023092258-clothing-passerby-e0f2@gregkh>
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From:   Saranya Muruganandam <saranyamohan@google.com>
Date:   Fri, 22 Sep 2023 11:21:10 -0700
Message-ID: <CAP9s-SrHMFD6Q8t9Htk8W5OrQTAoe2D51ZRf-Zap4O_3E485LA@mail.gmail.com>
Subject: Re: [PATCH] block: fix use-after-free of q->q_usage_counter
To:     Greg KH <gregkh@linuxfoundation.org>
Cc:     Jens Axboe <axboe@kernel.dk>, Tejun Heo <tj@kernel.org>,
        Ming Lei <ming.lei@redhat.com>, stable@vger.kernel.org,
        linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
        Zhang Wensheng <zhangwensheng@huaweicloud.com>,
        Zhong Jinghua <zhongjinghua@huawei.com>,
        Hillf Danton <hdanton@sina.com>, Yu Kuai <yukuai3@huawei.com>,
        Dennis Zhou <dennis@kernel.org>
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Apologies for leaving out the stable release info.
This is for both 5.10 and patch applies cleanly for 5.15.

I just sent out a (different) modified patch for 6.1 LTS.


On Fri, Sep 22, 2023 at 2:26=E2=80=AFAM Greg KH <gregkh@linuxfoundation.org=
> wrote:
>
> On Thu, Sep 21, 2023 at 11:20:12AM -0700, Saranya Muruganandam wrote:
> > From: Ming Lei <ming.lei@redhat.com>
> >
> > commit d36a9ea5e7766961e753ee38d4c331bbe6ef659b upstream.
> >
> > For blk-mq, queue release handler is usually called after
> > blk_mq_freeze_queue_wait() returns. However, the
> > q_usage_counter->release() handler may not be run yet at that time, so
> > this can cause a use-after-free.
> >
> > Fix the issue by moving percpu_ref_exit() into blk_free_queue_rcu().
> > Since ->release() is called with rcu read lock held, it is agreed that
> > the race should be covered in caller per discussion from the two links.
> >
> > Backport-notes: Not a clean cherry-pick since a lot has changed,
> > however essentially the same fix.
> >
> > Reported-by: Zhang Wensheng <zhangwensheng@huaweicloud.com>
> > Reported-by: Zhong Jinghua <zhongjinghua@huawei.com>
> > Link: https://lore.kernel.org/linux-block/Y5prfOjyyjQKUrtH@T590/T/#u
> > Link: https://lore.kernel.org/lkml/Y4%2FmzMd4evRg9yDi@fedora/
> > Cc: Hillf Danton <hdanton@sina.com>
> > Cc: Yu Kuai <yukuai3@huawei.com>
> > Cc: Dennis Zhou <dennis@kernel.org>
> > Fixes: 2b0d3d3e4fcf ("percpu_ref: reduce memory footprint of percpu_ref=
 in fast path")
> > Signed-off-by: Ming Lei <ming.lei@redhat.com>
> > Link: https://lore.kernel.org/r/20221215021629.74870-1-ming.lei@redhat.=
com
> > Signed-off-by: Jens Axboe <axboe@kernel.dk>
> > Signed-off-by: Saranya Muruganandam <saranyamohan@google.com>
> > ---
> >  block/blk-core.c  | 2 --
> >  block/blk-sysfs.c | 2 ++
> >  2 files changed, 2 insertions(+), 2 deletions(-)
>
> What stable kernel(s) are you expecting this backport to be applied to?
>
> thanks,
>
> greg "not a mind reader" k-h