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Subject: Re: [PATCH v2] nvme-tcp: Check if request has started before
 processing it
To:     Daniel Wagner <dwagner@suse.de>, linux-nvme@lists.infradead.org
Cc:     linux-kernel@vger.kernel.org, Jens Axboe <axboe@fb.com>,
        Hannes Reinecke <hare@suse.de>,
        Keith Busch <kbusch@kernel.org>, Christoph Hellwig <hch@lst.de>
References: <20210301175601.116405-1-dwagner@suse.de>
From:   Sagi Grimberg <sagi@grimberg.me>
Message-ID: <6b51a989-5551-e243-abda-5872411ec3ff@grimberg.me>
Date:   Fri, 5 Mar 2021 11:57:30 -0800
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> blk_mq_tag_to_rq() always returns a request if the tag id is in a
> valid range [0...max_tags). If the target replies with a tag for which
> we don't have a request but it's not started, the host will likely
> corrupt data or simply crash.
> 
> Add an additional check if the a request has been started if not
> reset the connection.
> 
> This addition check will not protected against an invalid tag which
> maps to a request which has been started. There is nothing we can do
> about this. Though it will at a least protect from crashing the host,
> which generally thought to be the right thing to do.

Daniel, again, there is nothing specific about this to nvme-tcp,
this is a safeguard against a funky controller (or a different
bug that is hidden by this). The same can happen in any other
transport so I would suggest that if this is a safeguard we
want to put in place, we should make it a generic one.

i.e. nvme_tag_to_rq() that _all_ transports call consistently.