linux-kernel - Re: [PATCH v2 6/6] block: skip queue if NULL on blk_cleanup

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Date:   Thu, 15 Jul 2021 08:11:57 +0100
From:   Christoph Hellwig <hch@...radead.org>
To:     Luis Chamberlain <mcgrof@...nel.org>
Cc:     axboe@...nel.dk, hare@...e.de, bvanassche@....org,
        ming.lei@...hat.com, hch@...radead.org, jack@...e.cz,
        osandov@...com, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 6/6] block: skip queue if NULL on blk_cleanup_queue()

On Wed, Jul 14, 2021 at 09:55:31PM -0700, Luis Chamberlain wrote:
> Now that error handling for add_disk*() calls is added, we must
> accept a common form for when errors are detected on the the
> add_disk*() calls, and that is to call blk_cleanup_disk() on
> error always. One of the corner cases possible is a driver bug
> where the queue is already gone and we cannot blk_get_queue(),
> and so may be NULL. When blk_cleanup_disk() is called in this
> case blk_cleanup_queue() will crash with a null dereference.
> 
> Make this an accepted condition and just skip it. This allows us
> to also test for it safely with error injection.

So you plan to call blk_cleanup_disk when add_disk fails?

For all drivers using blk_alloc_disk/blk_mq_alloc_disk there should
always be a queue.  The others ones aren't ready to handle errors
from add_disk yet in any way I think (and I plan to fix this up
ASAP).