Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Mon, 26 Dec 2022 12:18:48 +0100
From:   Jan Kara <jack@suse.cz>
To:     Yu Kuai <yukuai1@huaweicloud.com>
Cc:     paolo.valente@linaro.org, axboe@kernel.dk, jack@suse.cz,
        linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
        yukuai3@huawei.com, yi.zhang@huawei.com
Subject: Re: [PATCH] block, bfq: fix uaf for bfqq in bfq_exit_icq_bfqq
Message-ID: <20221226111848.oorzy2mecnrignzc@quack3>
References: <20221226030605.1437081-1-yukuai1@huaweicloud.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20221226030605.1437081-1-yukuai1@huaweicloud.com>
Precedence: bulk

On Mon 26-12-22 11:06:05, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@huawei.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@redhat.com>
> Signed-off-by: Yu Kuai <yukuai3@huawei.com>

Thanks for the patch! Feel free to add:

Reviewed-by: Jan Kara <jack@suse.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@suse.com>
SUSE Labs, CR