From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ming Lei <ming.lei@redhat.com>
Subject: Re: [PATCH -next v2] blk-throttle: Set BIO_THROTTLED when bio has
 been throttled
Date: Wed, 2 Mar 2022 21:51:13 +0800
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To: Laibin Qiu <qiulaibin@huawei.com>
Cc: tj@kernel.org, axboe@kernel.dk, cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org

On Tue, Mar 01, 2022 at 08:39:19PM +0800, Laibin Qiu wrote:
> 1.In current process, all bio will set the BIO_THROTTLED flag
> after __blk_throtl_bio().
> 
> 2.If bio needs to be throttled, it will start the timer and
> stop submit bio directly. Bio will submit in
> blk_throtl_dispatch_work_fn() when the timer expires.But in
> the current process, if bio is throttled. The BIO_THROTTLED
> will be set to bio after timer start. If the bio has been
> completed, it may cause use-after-free blow.
> 
> BUG: KASAN: use-after-free in blk_throtl_bio+0x12f0/0x2c70
> Read of size 2 at addr ffff88801b8902d4 by task fio/26380

After the queue lock is released, the bio can be dispatched & completed,
so it shouldn't be touched after lock release:

Reviewed-by: Ming Lei <ming.lei@redhat.com>

Thanks,
Ming