linux-kernel - Re: [PATCH] blk-mq: fix tags UAF when shrink nr_hw

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Message-ID: <98a47b9b-45ee-4166-aad7-6a2c05c201a0@suse.de>
Date:   Fri, 8 Sep 2023 07:51:16 +0200
From:   Hannes Reinecke <hare@...e.de>
To:     chengming.zhou@...ux.dev, axboe@...nel.dk, ming.lei@...hat.com
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        Chengming Zhou <zhouchengming@...edance.com>,
        Yi Zhang <yi.zhang@...hat.com>
Subject: Re: [PATCH] blk-mq: fix tags UAF when shrink nr_hw_queues

On 9/8/23 02:57, chengming.zhou@...ux.dev wrote:
> From: Chengming Zhou <zhouchengming@...edance.com>
> 
> When nr_hw_queues shrink, we free the excess tags before realloc
> hw_ctxs for each queue, during that we may need to access those
> tags, like blk_mq_tag_idle(hctx) will access queue shared tags.
> 
> So slab-use-after-free caused and reported by KASAN. Fix it by
> moving the releasing of excess tags to the end.
> 
> Fixes: e1dd7bc93029 ("blk-mq: fix tags leak when shrink nr_hw_queues")
> Reported-by: Yi Zhang <yi.zhang@...hat.com>
> Closes: https://lore.kernel.org/all/CAHj4cs_CK63uoDpGBGZ6DN4OCTpzkR3UaVgK=LX8Owr8ej2ieQ@mail.gmail.com/
> Cc: Ming Lei <ming.lei@...hat.com>
> Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>
> ---
>   block/blk-mq.c | 13 +++++++------
>   1 file changed, 7 insertions(+), 6 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@...e.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@...e.de                              +49 911 74053 688
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