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Milne" To: Hannes Reinecke , Keith Busch , Sagi Grimberg Cc: Daniel Wagner , linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, Jens Axboe , Christoph Hellwig Date: Wed, 31 Mar 2021 17:01:41 -0400 In-Reply-To: References: <20210301175601.116405-1-dwagner@suse.de> <6b51a989-5551-e243-abda-5872411ec3ff@grimberg.me> <20210311094345.ogm2lxqfuszktuhp@beryllium.lan> <70af5b02-10c1-ab0b-1dfc-5906216871b4@grimberg.me> <2fc7a320c86f75507584453dd2fbd744de5c170d.camel@redhat.com> <20210330232813.GA1935968@dhcp-10-100-145-180.wdc.com> Mime-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210331_220152_533675_A7AAE464 X-CRM114-Status: GOOD ( 41.09 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Wed, 2021-03-31 at 09:11 +0200, Hannes Reinecke wrote: > 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. That would be great. BTW in the crash dump I am looking at now, it looks like pdu->command_id was zero in nvme_tcp_recv_data(), and blk_mq_tag_to_rq() returned a request struct that had not been used. So I think we do need to check that the tag was actually allocated. -Ewan > > Cheers, > > Hannes _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme