linux-kernel - Re: [PATCH v2] nvme-tcp: Check if request has started before processing it

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Message-ID: <6b51a989-5551-e243-abda-5872411ec3ff@grimberg.me>
Date:   Fri, 5 Mar 2021 11:57:30 -0800
From:   Sagi Grimberg <sagi@...mberg.me>
To:     Daniel Wagner <dwagner@...e.de>, linux-nvme@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, Jens Axboe <axboe@...com>,
        Hannes Reinecke <hare@...e.de>,
        Keith Busch <kbusch@...nel.org>, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v2] nvme-tcp: Check if request has started before
 processing it


> 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.