From: Keith Busch <kbusch@kernel.org>
To: Sagi Grimberg <sagi@grimberg.me>
Cc: "Ewan D. Milne" <emilne@redhat.com>,
Daniel Wagner <dwagner@suse.de>,
linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org,
Jens Axboe <axboe@fb.com>, Hannes Reinecke <hare@suse.de>,
Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v2] nvme-tcp: Check if request has started before processing it
Date: Tue, 30 Mar 2021 16:28:13 -0700 [thread overview]
Message-ID: <20210330232813.GA1935968@dhcp-10-100-145-180.wdc.com> (raw)
In-Reply-To: <ed3ccac0-79ed-fe10-89eb-d403820b4c6a@grimberg.me>
On Tue, Mar 30, 2021 at 10:34:25AM -0700, Sagi Grimberg wrote:
>
> > > It is, but in this situation, the controller is sending a second
> > > completion that results in a use-after-free, which makes the
> > > transport irrelevant. Unless there is some other flow (which is
> > > unclear
> > > to me) that causes this which is a bug that needs to be fixed rather
> > > than hidden with a safeguard.
> > >
> >
> > The kernel should not crash regardless of any network traffic that is
> > sent to the system. It should not be possible to either intentionally
> > of mistakenly contruct packets that will deny service in this way.
>
> This is not specific to nvme-tcp. I can build an rdma or pci controller
> that can trigger the same crash... I saw a similar patch from Hannes
> implemented in the scsi level, and not the individual scsi transports..
If scsi wants this too, this could be made generic at the blk-mq level.
We just need to make something like blk_mq_tag_to_rq(), but return NULL
if the request isn't started.
> I would also mention, that a crash is not even the scariest issue that
> we can see here, because if the request happened to be reused we are
> in the silent data corruption realm...
If this does happen, I think we have to come up with some way to
mitigate it. We're not utilizing the full 16 bits of the command_id, so
maybe we can append something like a generation sequence number that can
be checked for validity.
next prev parent reply other threads:[~2021-03-30 23:29 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-01 17:56 [PATCH v2] nvme-tcp: Check if request has started before processing it Daniel Wagner
2021-03-05 19:57 ` Sagi Grimberg
2021-03-11 9:43 ` Daniel Wagner
2021-03-15 17:16 ` Sagi Grimberg
2021-03-30 16:19 ` Ewan D. Milne
2021-03-30 17:34 ` Sagi Grimberg
2021-03-30 23:28 ` Keith Busch [this message]
2021-03-31 7:11 ` Hannes Reinecke
2021-03-31 21:01 ` Ewan D. Milne
2021-03-31 22:24 ` Sagi Grimberg
2021-04-01 6:20 ` Christoph Hellwig
2021-04-01 8:25 ` Sagi Grimberg
2021-03-31 22:37 ` Sagi Grimberg
2021-05-06 15:36 ` Hannes Reinecke
2021-05-07 20:26 ` Sagi Grimberg
2021-05-07 20:40 ` Keith Busch
2021-05-07 23:22 ` Sagi Grimberg
2021-05-08 0:03 ` Keith Busch
2021-05-09 11:30 ` Hannes Reinecke
2021-05-11 18:16 ` Sagi Grimberg
2021-05-17 14:58 ` Daniel Wagner
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