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Date: Thu, 13 Nov 2025 15:44:55 +0100
From: Christoph Hellwig <hch@lst.de>
To: Damien Le Moal <dlemoal@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
	Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>,
	Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 1/3] block: fix NULL pointer dereference in
 blk_zone_reset_all_bio_endio()
Message-ID: <20251113144455.GA30779@lst.de>
References: <20251113134028.890166-1-dlemoal@kernel.org> <20251113134028.890166-2-dlemoal@kernel.org>
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On Thu, Nov 13, 2025 at 10:40:26PM +0900, Damien Le Moal wrote:
> For zoned block devices that do not need zone write plugs (e.g. most
> device mapper devices that support zones), the disk hash table of zone
> write plugs is NULL. For such devices, blk_zone_reset_all_bio_endio()
> should not attempt to scan this has table as that causes a NULL pointer
> dereference.
> 
> Fix this by checking that the disk does have zone write plugs using the
> atomic counter. This is equivalent to checking for a non-NULL hash table
> but has the advantage to also speed up the execution of
> blk_zone_reset_all_bio_endio() for devices that do use zone write plugs
> but do not have any plug in the hash table (e.g. a disk with only full
> zones).
> 
> Fixes: efae226c2ef1 ("block: handle zone management operations completions")
> Reported-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
> Signed-off-by: Damien Le Moal <dlemoal@kernel.org>

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

although maybe factoring that loop into helper might be a tad cleaner?