linux-kernel - Re: [PATCH] block, bfq: fix uaf for bfqq in bfq_exit_icq

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Date:   Mon, 26 Dec 2022 12:18:48 +0100
From:   Jan Kara <jack@...e.cz>
To:     Yu Kuai <yukuai1@...weicloud.com>
Cc:     paolo.valente@...aro.org, axboe@...nel.dk, jack@...e.cz,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        yukuai3@...wei.com, yi.zhang@...wei.com
Subject: Re: [PATCH] block, bfq: fix uaf for bfqq in bfq_exit_icq_bfqq

On Mon 26-12-22 11:06:05, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@...wei.com>
> 
> Commit 64dc8c732f5c ("block, bfq: fix possible uaf for 'bfqq->bic'")
> will access 'bic->bfqq' in bic_set_bfqq(), however, bfq_exit_icq_bfqq()
> can free bfqq first, and then call bic_set_bfqq(), which will cause uaf.
> 
> Fix the problem by moving bfq_exit_bfqq() behind bic_set_bfqq().
> 
> Fixes: 64dc8c732f5c ("block, bfq: fix possible uaf for 'bfqq->bic'")
> Reported-by: Yi Zhang <yi.zhang@...hat.com>
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>

Thanks for the patch! Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  block/bfq-iosched.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
> index 16f43bbc575a..ccf2204477a5 100644
> --- a/block/bfq-iosched.c
> +++ b/block/bfq-iosched.c
> @@ -5317,8 +5317,8 @@ static void bfq_exit_icq_bfqq(struct bfq_io_cq *bic, bool is_sync)
>  		unsigned long flags;
>  
>  		spin_lock_irqsave(&bfqd->lock, flags);
> -		bfq_exit_bfqq(bfqd, bfqq);
>  		bic_set_bfqq(bic, NULL, is_sync);
> +		bfq_exit_bfqq(bfqd, bfqq);
>  		spin_unlock_irqrestore(&bfqd->lock, flags);
>  	}
>  }
> -- 
> 2.31.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR