linux-kernel - Re: [PATCH] blk-mq: fix possible NULL pointer access in classic polling

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Message-ID: <Y5yLgydd0dk/I7wT@kbusch-mbp.dhcp.thefacebook.com>
Date:   Fri, 16 Dec 2022 08:15:15 -0700
From:   Keith Busch <kbusch@...nel.org>
To:     huteng19901016@...il.com
Cc:     axboe@...nel.dk, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, "huteng.ht" <huteng.ht@...edance.com>
Subject: Re: [PATCH] blk-mq: fix possible NULL pointer access in classic
 polling

On Fri, Dec 16, 2022 at 11:06:36PM +0800, huteng19901016@...il.com wrote:
> From: "huteng.ht" <huteng.ht@...edance.com>
> 
> Since poll method in blk_mq_ops may not be implemented by driver,
> add a judgement to avoid NULL pointer access.

Have you actually observed this NULL pointer access occur? Because the
poll attempt should have been abandoned much earlier due to the queue
not having QUEUE_FLAG_POLL set. If a driver has that flag set without
actually implementing ->poll(), though, that'd be a different bug.