From: Hannes Reinecke <hare@suse.de>
To: Keith Busch <kbusch@kernel.org>, 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>, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v2] nvme-tcp: Check if request has started before processing it
Date: Wed, 31 Mar 2021 09:11:59 +0200 [thread overview]
Message-ID: <e4bee13c-647a-55ff-2017-27ccfc314973@suse.de> (raw)
In-Reply-To: <20210330232813.GA1935968@dhcp-10-100-145-180.wdc.com>
On 3/31/21 1:28 AM, Keith Busch wrote:
> 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.
>
... which will be near impossible.
We can protect against crashing on invalid frames.
We can _not_ protect against maliciously crafted packets referencing any
random _existing_ tag; that's what TLS is for.
What we can do, though, is checking the 'state' field in the tcp
request, and only allow completions for commands which are in a state
allowing for completions.
Let's see if I can whip up a patch.
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@suse.de +49 911 74053 688
SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), GF: Felix Imendörffer
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next prev parent reply other threads:[~2021-03-31 7:12 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
2021-03-31 7:11 ` Hannes Reinecke [this message]
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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