linux-kernel - Re: [PATCH 0/8]: blk-mq: use static

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Message-ID: <1552930085.152266.36.camel@acm.org>
Date:   Mon, 18 Mar 2019 10:28:05 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Jianchao Wang <jianchao.w.wang@...cle.com>, axboe@...nel.dk
Cc:     hch@....de, jthumshirn@...e.de, hare@...e.de, josef@...icpanda.com,
        sagi@...mberg.me, keith.busch@...el.com, jsmart2021@...il.com,
        linux-block@...r.kernel.org, linux-nvme@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/8]: blk-mq: use static_rqs to iterate busy tags

On Fri, 2019-03-15 at 16:57 +0800, Jianchao Wang wrote:
> [2] https://marc.info/?l=linux-block&m=154526189023236&w=2

Hi Jianchao,

That is a reference to the "BUG: KASAN: use-after-free in bt_iter" issue.
I think that issue can be fixed in another way than modifying all code that
iterates over tags, namely by adding an rcu_read_lock() / rcu_read_unlock()
pair in bt_for_each() and bt_tags_for_each() and by changing the calls in
blk_mq_free_rqs() and blk_free_flush_queue() that free the data structures
used by the tag iteration functions into kfree_rcu() or call_rcu() calls.

Thanks,

Bart.